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Tire and alignment discussion


Cueball1

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Admin note:  The following posts were moved from within a thread in the Politics, Religion & Controversy subforum.  As a result, some comments may not make sense as they reference posts in the original thread; however, this tangential conversation is good content worth exposing in the proper subforum.
 
-JohnCh

 

Maybe a return to what we all have in common, a love for 7s and helping others is what's needed here? 😉

 

Needing track wheels and tires for my beautiful Birkin.  I'm thinking 15" as there's a wider variety of both wheels and tires available.  Thinking 7" and 195 in front.  9" and 225 in the rear.  Seems to be a popular stagger of sizes.  Open to suggestions if you think differently!

 

For tires, communication, feel and reasonable durability are priorities, not needing the fastest possible tire.  Any suggestions?  There's so many more manufacturers and models than when i was doing a lot track days 10-15 years ago. 

 

 

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On 1/24/2024 at 2:58 PM, Cueball1 said:

Thanks Bruce. As I was involved in the initial discord I was simply hoping to lighten the mood.  Will look into avons!  Wheel and tire sizes seem correct? 

@Cueball1 -  sorry for the late response - I just noticed your question.

 

I don't think the two inch drop will be a problem.  Croc has more track knowledge than I, so he would be a better party to interrogate on this matter.  IMO, it is vital to keep a balance up front between push AKA understeer (the front tires slide out) and oversteer (the front tires grab so well, and/or rear traction is compromised, so that the car pivots around the front tires).  Personally, I prefer a car with just a bit of push at the extremes, and a car that is quickly salvageable when oversteer hits.  The front tire treatment ties into the rear - too wide in back will detract from your ability to move the car around, eliminate throttle steer, and encourage understeer.  In your case, based on my experience, I would use a bit more width in the front, say 7.5 inches, not so you can fit a bigger tire, but to firm up the tire on the wheel, so it can grip the track surface better instead of rolling over.

 

On track with my S2K, I used symmetric racing wheels and tires all around - (from memory:) 13" diameter wheels by 10" wide with Hoosier racing slicks.  The car stuck like glue and went like hell.  It would push and sometimes oversteer if the tires were cold, and because of the light overall weight, sometimes the better part of two laps was required to heat them up.

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On 1/24/2024 at 12:21 AM, Cueball1 said:

Needing track wheels and tires for my beautiful Birkin.  I'm thinking 15" as there's a wider variety of both wheels and tires available.  Thinking 7" and 195 in front.  9" and 225 in the rear.  Seems to be a popular stagger of sizes.  Open to suggestions if you think differently!

 

For tires, communication, feel and reasonable durability are priorities, not needing the fastest possible tire.  Any suggestions?  There's so many more manufacturers and models than when i was doing a lot track days 10-15 years ago.

 

 

11 hours ago, Bruce K said:

Croc has more track knowledge than I, so he would be a better party to interrogate on this matter. 

 

Why not see if I can start the traditional USA7s thread drift by going off topic in the middle of someone else's foodfight.  I like your thinking @Cueball1 especially since I feel guilty for starting this little boys pissing contest although I have now had a golden shower and dried myself off. 

 

Bruce touches on these points in his earlier comments - I'm just going to reorder and expand slightly. 

 

If you are going for an extra set of wheels then the choice between 15" and 13" is open to consider.  However, I just realized you have a Birkin and I don't think the calipers/hubs accept a 13" wheel?  I vaguely recall Tom Carlin doing some modification to make it work on another forum member's Birkin track car.   He does track days in his demonstrator Birkin on 15 inch wheels. 

 

The transformation of a se7en's handling going from 15" to 13" is profound.  Lighter rotational mass means things spool up quicker and the handling is much better.  I find the breakaway point is telegraphed much better as the driver gets a better feel of what grip levels are.  In an ideal world I would show you what it is like in a back to back test - it was eye opening the first time I did it.   Either way, this is your first decision point - which diameter wheels to select (assuming the Birkin gives you the choice).

 

Decision two is then width of the wheels.  Birkins traditionally run a square set up for wheel width.  Caterham is square up to around 180hp then they go stagger set up after that where rears are wider than the fronts.   The wider rears becomes important with more hp as you are trying to put the power down PLUS control corner rotation.  Too wide on a lower hp car and you cannot keep the car nimble to rotate it in corners.  By rotate I mean pivot the car not spin it.  All cars have mechanical grip so you can throw a se7en into a corner and carve your way around using that mechanical grip.  However, that only works up to a certain speed.  To add speed beyond that you need to know how to corner beyond the limits of just carving an arc around and starting to adapt the grip at the wheels to pivot the car in a corner.  That requires a level of slip that is simply not possible if you stuck fat wide tires on a lower hp car.  Some will disagree but I find a se7en handles better and can be faster with a slightly less tire than you think you need.  Earlier in my driving history when I was less experienced I preferred feeling safe on mechanical grip but that puts a ceiling on your speed potential which you need to go through to be a better driver.  The Speed Secrets series of books by Ross Bentley describes this far better than I can - get volume 1 and have a read.  I think you have a Duratec Birkin so should be north of 200hp?  The other thing to consider is what fits under your rear wings.  Will a wider stagger set up rub the rear wing.  I have seen a race/track Birkin with a stagger set up rub a hole in the top of the rear wing, partly from tight clearances, and partly as the traditional road se7en suspension is fairly soft (as it should be) since you use that to accentuate weight transfer around the individual wheels on a light car.

 

Decision 3 is then what tires.  A se7en is a lightweight car.  The lighter the tires the lower the unsprung weight and the better the handling.  Avons traditionally have a light tire carcass compared with the alternatives - roughly a 20% lighter than the equivalents from a competitor like Toyo or Yokohama.  Thats why you see a lot of people gravitate to Avons in the UK and even here in the US.  The Avon compounds are usually faster.  Last year at Spa, on Avon ZZRs in the dry, I could lap seconds quicker than a race 420R that was running on Toyos with a driver.  That should not be possible as the race car was much lighter than my road 420R, plus it had a sequential and better gearing and a driver who I rate better than me.  Decisions 1 and 2 will inform the population of tires you have to choose from.  I have heard Roger Krause Tires reocmmending Nittos and Kumhos from time to time but I don't have experience with those brands although I know Roger and his team know their tires better than anyone else I have found in the US.

 

For track, the fastest option will always be a slick.  I use Hoosier slicks on my US Caterham for track work.  They hardly heat cycle given the light weight and it is easy to stretch 1-1.5 years of track time out of them.  A few I know have been using Michelin formula opening wheel slick tires and like them.  I am sure there are other slick choice but I like the Hoosiers.  However, if you are not experienced with a lot of track time then I would not recommend a slick tire.  They take you up to silly speed grip such that when it lets go its going to be messy.  Slicks do not telegraph their break point to a driver as well as a road tire.  Track experience helps here.

 

So then you drop back to the road types of tires.  The Avon ZZR has three compounds to choose from and all 3 are faster on track than anything else out there that is not a slick.  However, it is not a good option on wet tracks as it gives up fairly quickly.  Avon ZZS is a road legal tire and is good in both wet and dry and produces roughly similar lap times to the usual choices you will be able to get from Toyo or Yokohama.  For my UK Caterham I run the Avon ZZR extreme compound as my dry weather tire and the Avon ZZS as my wet weather track tire.  Hoosiers are not available in the UK plus UK/European track day operators ban slicks so they were never an option there.  Even so the Avon ZZR is pretty close to the Hoosier from back to back testing - roughly 1-2 seconds a lap slower around a 1.9 mile circuit like NJMP Lightning.   I have used the Avon ZZS in all conditions on track - monsoon, rain, snow, ice and dry and they are a very good all rounder.   The Avon ZZS is roughly 3-4 seconds a lap slower around NJMP Lightning than the Avon ZZR) and is going to be comparable to what a similar sized Toyo/Yokohama performance tire for a seven can do.

 

Don't get hung up too much on change in rolling diameter.  You should measure the rolling diameter on your rear road tire set up now and compare it to what you are going to get on your track tire set up.  If it is smaller then yes your odometer will click over quicker but remember you just shortened the gearing so the car is accelerating quicker and you have a lower top speed.   Quicker acceleration out of the corners is a good thing.  Lower top speed is probably irrelevant.   I don't know what your local track will be but it is unlikely you will see Vmax speed down the straight.  Unless it is a pro car where the gearing is calibrated to the track to be peak engine speed for optimum lap times or at big straight track like Spa-Francorchamps/banked oval, every other car is not reaching their top speed on the average race track.  The average new Corvette will pull 150-160mph down the straight at NJMP but it can do 175mph+.  The same applies to a seven.   When I go from the 15 inch road wheels with Avon ZZS on my CSR to the 13 inch track wheels with Hooser slicks, the rear rolling diameter comes down less than a quarter of an inch.  The improvement in track performance is monumentally improved.  I now find the car will almost redline in 6th gear down the NJMP straights.  I'm not even close to doing that on the road wheel set up, I was at least 1000rpm short.  Theoretical Vmax comes down from 155mph to around 140mph area.  Of course if you increase rolling diameter the opposite will happen - slower acceleration and higher top speed.  My critical observation here is a seemingly small change in rear rolling diameter will produce a magnified effect on our lightweight cars.  Its hard to know until you try it.  But it is unlikely to become an important factor in your driving on track.

 

If this was a Caterham with 220hp then I would be going 13 inch wheels, 7inch wide fronts, 8.5/9 inch rears and Avon ZZS all rounders for my versatile all weather track tire.  If the Caterham was below 200hp then I would go 7 inch allround width but rest the same.

 

For a Birkin, while you need to validate this, I would be betting you will end up on 15 inch track wheels and likely a square 8 inch set up (or a stagger 7 front and 8 rear set up) with a good menu of Avon ZZS, Toyos or Yokos to choose from that will make you happy with the outcome.

 

 

 

 

 

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@Crocwow!  Amazing information.  Traveling today, just boarded a plane, so it will take me a bit to respond properly.

 

My car puts 187 to the rear wheels so is something like 215ish hp.  George Hillard, the original owner, ran staggered 13" kodiaks with hoosiers so 13" should work.  I do want a more forgiving breakaway than hoosiers likely offer.  Have maybe 20 track days and a couple Lemons races under my belt.  Track days were in my 250hp turbo'd Miata.  Light for a road car but a pig compared to 7s.

 

Will give your fantastically thorough response a proper go through and consideration when I have some down time over the next day.  Thank you so much!  

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5 hours ago, Cueball1 said:

@Crocwow!  Amazing information.  Traveling today, just boarded a plane, so it will take me a bit to respond properly.

 

My car puts 187 to the rear wheels so is something like 215ish hp.  George Hillard, the original owner, ran staggered 13" kodiaks with hoosiers so 13" should work.  I do want a more forgiving breakaway than hoosiers likely offer.  Have maybe 20 track days and a couple Lemons races under my belt.  Track days were in my 250hp turbo'd Miata.  Light for a road car but a pig compared to 7s.

 

Will give your fantastically thorough response a proper go through and consideration when I have some down time over the next day.  Thank you so much!  

 

 

Ahhhh....I remember this car.  Maroon Birkin.  George brought it to NJMP once.  Beautifully prepared.  He did do some sort of modification to take 13 inch wheels as I remember him telling me about the various modifications he had done to make it better as a track car.  This is the first of only two Birkins I have ever seen run 13 inch wheels.  At 210fwhp you should be fine on a stagger set up.   I definitely think you will prefer a 13 inch wheel on track over the 15 inch option which is usually a better road solution.  Just aim to keep somewhat close on the rear wheel rolling diameter (i.e. your regular road tire sizing will be a proxy to help match on a 13 inch solution) - there are online calculators to help you with this.  

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@Croc

 

I'm in regular communication with George.  Tracked him down after buying the car from the orthodontist he sold it to. He's sent me all sorts of history and albums of pics of the car. He definitely loved that car! I will ask him asap about what was needed to run 13s.  

 

My main thought on going with 15s is it gives me access to a much wider variety of both wheels and tires.  Pretty much any wheel that fits a miata should work.  Lots of relatively light and affordable options for 15" wheels.  There's also a whole new crop of companies making dot approved track tires but often 15" is the smallest size they make.

 

You pretty much have me convinced avon and 13" wheels are the way to go though.  Feel is everything. I'm a decent driver, was typically in whatever the advanced group was back when I was a regular at hpde days, but I'm no pro. A communicative and forgiving tire, along with a definite sense of my own mortality, will go a long way in keeping me from stupid mistakes. 

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On 1/26/2024 at 7:31 AM, Croc said:

 

If you are going for an extra set of wheels then the choice between 15" and 13" is open to consider.  However, I just realized you have a Birkin and I don't think the calipers/hubs accept a 13" wheel?  I vaguely recall Tom Carlin doing some modification to make it work on another forum member's Birkin track car.   He does track days in his demonstrator Birkin on 15 inch wheels. 

The transformation of a se7en's handling going from 15" to 13" is profound.  Lighter rotational mass means things spool up quicker and the handling is much better.  I find the breakaway point is telegraphed much better as the driver gets a better feel of what grip levels are.  In an ideal world I would show you what it is like in a back to back test - it was eye opening the first time I did it.   Either way, this is your first decision point - which diameter wheels to select (assuming the Birkin gives you the choice).

...

 

Do you have any experience with Sevens tramlining after moving 13" -> 15", or wider tires, or modern compounds?  My Seven left the factory with 13" Panasports, but came to me with modern 14.5lb 15x7/15x8s with 888Rs.  Visually they do suit the car and drop a decade or two from its looks.  But, as delivered, I've never see a car more desperate to explore the full possibilities of every single road imperfection!  We've since shared some quality time on the setup pad and the problem has dropped from diabolical to just distracting.

 

My next step is to reduce the front tire width.  What would you anticipate on a 255whp Seven?

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17 hours ago, Marek said:

 

Do you have any experience with Sevens tramlining after moving 13" -> 15", or wider tires, or modern compounds?  My Seven left the factory with 13" Panasports, but came to me with modern 14.5lb 15x7/15x8s with 888Rs.  Visually they do suit the car and drop a decade or two from its looks.  But, as delivered, I've never see a car more desperate to explore the full possibilities of every single road imperfection!  We've since shared some quality time on the setup pad and the problem has dropped from diabolical to just distracting.

 

My next step is to reduce the front tire width.  What would you anticipate on a 255whp Seven?


 

I will respond here despite the presence of an ongoing menage a trois elsewhere in this thread. Just avert your eyes.  
 

I am a little surprised about the tramlining as I have not heard that being an issue on any seven since Avon ACB10 tires were being used.  They were a bias ply motorsport (Formula Ford) tire and so had a convex profile across the tire.  
 

Other sevens do just fine on 15 inch wheels of the size you mention.  Plus they are what I would choose for the horsepower your car has.   I don’t get a ton of tramlining unless the road is really bad yet I have same size wheels and engine hp as you have but I have different brand of tire.  Reducing wheel width feels wrong to me with what you have said.  
 

Applying a process of elimination on the front wheels:

a) is it the R888s uniquely having the tramlining characteristic compared to say another brand of rubber?  Others have used this tire on many brands of seven and I cannot recall them complaining about tramlining.  
b) are you squeezing a too wide tire onto the size width wheel you have and inadvertently creating a convex cross section on the fronts?   
c) is it your set up?   What camber, caster and toe are you running?  Positive rake? 

 

Options b) or c) feel most likely with what you have said so far.  Reactions?

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5 hours ago, Croc said:


 

I will respond here despite the presence of an ongoing menage a trois elsewhere in this thread. Just avert your eyes.  
 

I am a little surprised about the tramlining as I have not heard that being an issue on any seven since Avon ACB10 tires were being used.  They were a bias ply motorsport (Formula Ford) tire and so had a convex profile across the tire.  
 

Other sevens do just fine on 15 inch wheels of the size you mention.  Plus they are what I would choose for the horsepower your car has.   I don’t get a ton of tramlining unless the road is really bad yet I have same size wheels and engine hp as you have but I have different brand of tire.  Reducing wheel width feels wrong to me with what you have said.  
 

Applying a process of elimination on the front wheels:

a) is it the R888s uniquely having the tramlining characteristic compared to say another brand of rubber?  Others have used this tire on many brands of seven and I cannot recall them complaining about tramlining.  
b) are you squeezing a too wide tire onto the size width wheel you have and inadvertently creating a convex cross section on the fronts?   
c) is it your set up?   What camber, caster and toe are you running?  Positive rake? 

 

Options b) or c) feel most likely with what you have said so far.  Reactions?

 

<eyes averted>

 

I see I missed a detail.  Rubber on the car is 225/50-15, 235/50-15.  A 225 is the limit for a 7" wheel - so some curve across the contact patch is a possibility as you suggest.

 

Camber as delivered was 1 ⅓ degree.  Now decreased to ⅓ degree.

Toe was 1/16".  Now increased to ⅛".

The new settings are tame and non-controversial; so unlikely to be a major factor.

 

The current R888Rs are the only rubber I've had on the car (and they are old), so fresh tires will go on this spring.  R888Rs are a known quantity and seem very unlikely to be part of the problem.  Which brings the question back to tire width.  I've been thinking 205 or 215 and your comment on curvature reinforces my suspicion the 225s on a 7" are the root cause.

 

As for tire construction, I am curious if you have any insights into how sensitive these cars are to the squareness of the tire shoulder.  Though the R888R is not unusually square - so unlikely to be a factor here.

 

Thanks for sharing some wisdom!

 

</eyes averted>

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9 hours ago, Marek said:

I see I missed a detail.  Rubber on the car is 225/50-15, 235/50-15.  A 225 is the limit for a 7" wheel - so some curve across the contact patch is a possibility as you suggest.

 

Camber as delivered was 1 ⅓ degree.  Now decreased to ⅓ degree.

Toe was 1/16".  Now increased to ⅛".

The new settings are tame and non-controversial; so unlikely to be a major factor.

 

The current R888Rs are the only rubber I've had on the car (and they are old), so fresh tires will go on this spring.  R888Rs are a known quantity and seem very unlikely to be part of the problem.  Which brings the question back to tire width.  I've been thinking 205 or 215 and your comment on curvature reinforces my suspicion the 225s on a 7" are the root cause.

 

As for tire construction, I am curious if you have any insights into how sensitive these cars are to the squareness of the tire shoulder.  Though the R888R is not unusually square - so unlikely to be a factor here.

 

Set up for camber and toe-in spec is where I would expect them.  It is toe in and not toe out?  You don't mention caster or rake.  Some positive rake of 10-15mm is always good.  I expect you would have caster in the 5-6 degree range. 

 

Even so, I am not seeing anything there that looks to be driving substantial tramlining.

 

The tire size on the front is a flashing red light to me.  Given the R888 sidewalls are very much stronger (less flexible) than the sidewalls on the equivalent Avons (which are a lighter weight construction of carcass), I think you have created the convex profile that is likely causing your tramlining experience.  The R888s were designed for a much heavier car than a seven.  Much heavier than even the Avons were intended.  So they flex less.  The common way people got around that was to lower the tire pressures to absurdly low levels (think 14psi).  So while I run 18psi cold on  Avon ZZR/ZZS (which translates to 24-25psi when at ideal target hot temps), the R888 would need to go lower cold psi in order to make the sidewalls flex more and generate more heat into the tire.

 

These cars are sensitive to tire profile squareness and this is a function of adapting a modern saloon car tire onto a car less than half the weight of the regular saloon car.  We normally adjust for that by lowering the tire pressures.

 

If I were you I would run an experiment.   Drop tire pressures all round to 15psi and (carefully) see what that does to your tramlining.  Try again (carefully) at 12-13psi and compare results.  If my theory is right then you should see less tramlining as the car weight is flexing the sidewalls to get to a better profile cross section.  The concern I have at a 12 psi you can induce enough cornering force to rip the bead off the rim.  But as you are testing tramlining (i.e. a straight ahead feel) the risk of that happening should be minimal as you should not be cornering hard for this experiment.  This should give some feedback on whether a wheel width size change is needed or not. 

 

If it does improve it then that gives us the insight that tire sidewall stiffness is the issue.  The its a matter of choosing a Avon for a more flexible sidewall or if you want to stay on the existing R888 front tire sizing then maybe a square set up with 8 inch wide wheels all round?    I definitely would not be going narrower wheels with your horsepower. 

 

 

 

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15 hours ago, Croc said:

 

Set up for camber and toe-in spec is where I would expect them.  It is toe in and not toe out?  You don't mention caster or rake.  Some positive rake of 10-15mm is always good.  I expect you would have caster in the 5-6 degree range. 

 

Even so, I am not seeing anything there that looks to be driving substantial tramlining.

 

The tire size on the front is a flashing red light to me.  Given the R888 sidewalls are very much stronger (less flexible) than the sidewalls on the equivalent Avons (which are a lighter weight construction of carcass), I think you have created the convex profile that is likely causing your tramlining experience.  The R888s were designed for a much heavier car than a seven.  Much heavier than even the Avons were intended.  So they flex less.  The common way people got around that was to lower the tire pressures to absurdly low levels (think 14psi).  So while I run 18psi cold on  Avon ZZR/ZZS (which translates to 24-25psi when at ideal target hot temps), the R888 would need to go lower cold psi in order to make the sidewalls flex more and generate more heat into the tire.

 

These cars are sensitive to tire profile squareness and this is a function of adapting a modern saloon car tire onto a car less than half the weight of the regular saloon car.  We normally adjust for that by lowering the tire pressures.

 

If I were you I would run an experiment.   Drop tire pressures all round to 15psi and (carefully) see what that does to your tramlining.  Try again (carefully) at 12-13psi and compare results.  If my theory is right then you should see less tramlining as the car weight is flexing the sidewalls to get to a better profile cross section.  The concern I have at a 12 psi you can induce enough cornering force to rip the bead off the rim.  But as you are testing tramlining (i.e. a straight ahead feel) the risk of that happening should be minimal as you should not be cornering hard for this experiment.  This should give some feedback on whether a wheel width size change is needed or not. 

 

If it does improve it then that gives us the insight that tire sidewall stiffness is the issue.  The its a matter of choosing a Avon for a more flexible sidewall or if you want to stay on the existing R888 front tire sizing then maybe a square set up with 8 inch wide wheels all round?    I definitely would not be going narrower wheels with your horsepower. 

 

 

 

 

I hadn't considered rake - my math says you are recommending ¼ - ⅓ degree of rake (I am accounting here for the slight differences in our wheelbases).

I don't have the caster numbers handy - but I will check those a well.

 

Which leaves us with tire fitment/construction/pressures.  From your comments, I am clearly running much too much pressure across the board; so your experiment is the right place to start.  12 psi is generally beadlock territory; but agreed it shouldn't be a problem for straight-line testing.

 

Wider front wheels or a 215 on the current wheels looks like where this is headed - preferably with a switch to Avons or maybe a similar LL rated tire.

 

Perhaps we'll have a break in temperatures in the next few weeks and I can report back the results.

 

 

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5 hours ago, Marek said:

 

I hadn't considered rake - my math says you are recommending ¼ - ⅓ degree of rake (I am accounting here for the slight differences in our wheelbases).

I don't have the caster numbers handy - but I will check those a well.

 

Which leaves us with tire fitment/construction/pressures.  From your comments, I am clearly running much too much pressure across the board; so your experiment is the right place to start.  12 psi is generally beadlock territory; but agreed it shouldn't be a problem for straight-line testing.

 

Wider front wheels or a 215 on the current wheels looks like where this is headed - preferably with a switch to Avons or maybe a similar LL rated tire.

 

Perhaps we'll have a break in temperatures in the next few weeks and I can report back the results.

 

 

 

I am sure you know this, but only play with rake if all else fails. One adjustment at a time, then test before deciding next adjustment.  Otherwise you get lost in your changes and creating new problems.  I know my CSR plus Westfields are sensitive to rake and often it is a solution when all else has failed. 

 

I will be interested to hear what happens from the experiment. 

 

 

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My car is a LoCost but the front suspension does not know that. I run 15x6 front and 15x7 rear loaded with 205 and 225 receptivity. I have no trouble with tram lining, the car is planted. I have run the R888 and the R888s. I much preferred the R888 but they no longer offer it in 15". With the much stiffer sidewall I always had problems getting the R888s up to temp, but I know others love them. I now use the Toyo RA1, I favorite with the Miata crowd. Softer side wall, easy to get up to temp and grip the best just before the cords show.  I have attached a picture of my alignment spec, it's a live rear axle car so the rear settings are not that adjustable. 

Alignment.jpg

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On 2/1/2024 at 6:31 AM, Croc said:

 

I am sure you know this, but only play with rake if all else fails. One adjustment at a time, then test before deciding next adjustment.  Otherwise you get lost in your changes and creating new problems.  I know my CSR plus Westfields are sensitive to rake and often it is a solution when all else has failed. 

 

I will be interested to hear what happens from the experiment. 

 

 

To close the loop....

 

Yes, ⅛" toe-IN.  Caster is 3 degree positive; which is the factory setting.

 

The dampers would likely benefit from a rebuild.  That won't cure the problem, but there is an outside chance it is magnifying it.

 

Looking at tire options, I am not finding a 215-15 in a suitable tire.  So staying with a 225 front and going to a soft sidewall might be the best option as a 205 seems a too drastic change.  But I am not finding options for 235 for the rear aside from the R888R.  Avons appear unobtainable.

 

A wider front wheel means a new set of wheels as the XXR 557 is no longer in production.  And that makes this a bigger problem.

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20 hours ago, Marek said:

Yes, ⅛" toe-IN.  Caster is 3 degree positive; which is the factory setting.

 

The dampers would likely benefit from a rebuild.  That won't cure the problem, but there is an outside chance it is magnifying it.

 

Those settings are conventional and not likely driving the tramlining.  The dampers may make it worse but its at the margins or under really hard acceleration. 

 

So I was bored on a 3 hour conference call today so went tire shopping for you.

 

I don't know what your objective for a tire is but assume you want performance and the odd track day.  Would assume you want DOT compliance for road use but thats your decision and responsibility. 

 

Just doing the front tires.  You have 225/50 on 15x7 rim.  That gives you a 23.9" diameter. 

 

Working backwards using the diameter +/- 1 inch to give me tire sizing and the diameter for that size I get:

 

225/45/15 23"

205/50/15 23.1"

225/50/15 23.9"

205/55/15 23.9"

195/60/15 24.2"

185/55/15 24.5"

 

I kept within +/- 1 inch as:

- You may have wing clearance issues on the upper end

- may create an unsightly visual gap on the low end

- different profile thicknesses may look goofy when looking at say a low profile rear. 

 

Then using the Tire Rack site to give me options by each size I get:

 

225/45/15 23"

https://www.tirerack.com/tires/TireSearchResults.jsp?width=225%2F&ratio=45&diameter=15&startIndex=0&search=true&pagelen=20&pagenum=1&pagemark=1&RunFlat=All

 

Options here:

  • Toyo Proxes R1R
  • Falken Azenis RT660
  • Continental Extreme Contact
  • Kumho Ecsta V730
  • Toyo Proxes R888R

 

205/50/15 23.1"

https://www.tirerack.com/tires/TireSearchResults.jsp?width=205%2F&ratio=50&diameter=15&startIndex=0&search=true&pagelen=20&pagenum=1&pagemark=1&RunFlat=All

 

Options here:

  • Toyo Proxes RA1
  • Falken Azenis RT660
  • Continental Extreme Contact
  • Kumho Ecsta V730
  • Toyo Proxes R888R
  • Goodyear Eagle F1 Supercar
  • Hoosier Radial wet W2
  • Dunlop Direzza Z111
  • Toyo Proxes R1R
  • Bridgestone Potenza RE-71RS
  • Yokohama Advan A052
  • Nanking Sport Nex CR-S
  • Yokohama Advan Neo AD09

 

225/50/15 23.9"

https://www.tirerack.com/tires/TireSearchResults.jsp?width=225%2F&ratio=50&diameter=15&startIndex=0&search=true&pagelen=20&pagenum=1&pagemark=1&RunFlat=All

 

Options here:

  • Toyo Proxes RA1
  • Toyo Proxes R888R
  • Bridgestone Potenza RE-71RS
  • Yokohama Advan A052

 

205/55/15 23.9"

https://www.tirerack.com/tires/TireSearchResults.jsp?width=205%2F&ratio=55&diameter=15&startIndex=0&search=true&pagelen=20&pagenum=1&pagemark=1&RunFlat=All

 

Option here is the Yokohama Advan Fleva V701

 

 

195/60/15 24.2"

https://www.tirerack.com/tires/TireSearchResults.jsp?width=195%2F&ratio=60&diameter=15&startIndex=0&search=true&pagelen=20&pagenum=1&pagemark=1&RunFlat=All

 

Snow tire land - ignore

 

 

185/55/15 24.5"

https://www.tirerack.com/tires/TireSearchResults.jsp?width=185%2F&ratio=55&diameter=15&startIndex=0&search=true&pagelen=20&pagenum=1&pagemark=1&RunFlat=All

 

Snow tire land - ignore

 

 

Now filtering that lot down to two primary size options and a short tire list for more serious consideration (with my annotations) for the fronts:

 

Option 1 - 205/50

 

  • Toyo Proxes RA1 - How do each of the Proxes RA1/R1R/R888 line up in order?  Softest is best for our cars as light weight is gentle.  RA1 is race so maybe the stickiest?
  • Falken Azenis RT660 - Dont know these
  • Continental Extreme Contact - Dont know these
  • Kumho Ecsta V730 - Dont know these
  • Toyo Proxes R888R - better sized option than current 225/50 but rolling diameter drops to 23.1"
  • Goodyear Eagle F1 Supercar - Don't know these but tread looks interesting a little too slick like?
  • Hoosier Radial wet W2 - track only - not DOT.   Likely not wear well and may overheat.  This would be a bold choice!  Very expensive.
  • Toyo Proxes R1R - Is RA1 softer than R1R or R888R?  Or other way around. 
  • Yokohama Advan A052 - Dont know these.
  • Nanking Sport Nex CR-S - People say good things about Nankings on Miatas in performance application?  Dark horse candidate?
  • Yokohama Advan Neo AD09  - Someone used these on a seven years ago.  Don't ask me to remember who!

 

 

Option 2 - 225/50

  • Toyo Proxes RA1 - refer my comments above re Proxes in general
  • Toyo Proxes R888R

 

@Marek  You will need to validate my thinking (or lack of) on tire diameter but I think thats your best range of options. 

 

Because I used Tirerack to see the broad range of options, Avon does not appear as they do not sell it.  Maybe a call to Roger Kraus Tires in CA to see what they have in sizing.  A phone call to them would be good as you could ask them what their opinion would be for the two size options you have.  They do primarily motorsports -track and autocross - and see a range of cars come through, including sevens.  They would have a better idea than the majority of participants in this thread. 

 

Have you seen this thread discussing similar thoughts on non-Avon tire options?

 

 

 

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I put 10K miles on my first Caterham using Proxes R1’s. Mostly street use but many track days as well. Good rain tire when new. Much improved grip as the tread wore down, though rain performance suffered.

 

The Yoko Advan AO52’s are excellent for combination street/ track on the much heavier Miatas that they are often paired with. Ditto the Falkens you mention.

 

I liked the R888R on my Caterham as well for street/track. Their decent tread makes them driveable in the rain and sticky rubber makes them good at the track(when warmed up, which doesn’t always happen with street use). Also will deposit much road debris in the cockpit….

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I ended up getting the Continental "ExtremeContact Force" for my WCM this year.  225/40/17 front (8 inch wheels) 245/40/17 rear (9 inch wheels).  They are supposed to be on par with the Hankook's but a little lower profile and less expensive.  Less grippy than the Falkens, but not as sensitive to heat cycling out.  These should work for me driving from home to the track, doing some hot laps, then driving home.

 

@Croc Hankook RS4's may also need to go on the list of options.  Tire rack doesn't seem to stock all of the sizes at the moment.

 

PXL_20240127_174820082.thumb.jpg.7bb9d2f8e1f1bdb4b5f860f078ee6790.jpgPXL_20240127_175038977.thumb.jpg.8d81e65bb5f04b1cf5fc5314e42d96b9.jpg

Edited by nc7s4
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