Autocross setup help

[dannykao]

Been to my 3rd autox event in the 7 on Saturday and I am getting more confused (or cleared, not sure which is more).

 

Thanks to Micheal D's A6, I got to run FF slicks and R-comp.

 

I also found out my top speed in 2nd gear is 58mph with 225/45/13s and about 63mph with 22.5x10-13s. Tom told me I might have the 3.9x final drive ratio instead of 3.6x, which should give me 5 more mph in the 2nd gear. Does anyone know off hand that Caterham or anyone that carries a pumpkin with lower final drive ratio with LSD built-in?

 

On stock (not wide track) suspension and 225/13 A6s, the car understeers quite a bit. On Formula Ford slicks with 3.5" backspacing, the car turns-in fine and steady state well; but very lose during transitions. (I was told to report back my findings by Michael D)

[Boxologist]

more camber?

 

as for the diff, call the Aldermans, Chip Bond, or Ben at CatUSA and get an accurate answer. It may be an interchangable ring gear.

[TheDingo8MyBaby]

 

I also found out my top speed in 2nd gear is 58mph with 225/45/13s and about 63mph with 22.5x10-13s. Tom told me I might have the 3.9x final drive ratio instead of 3.6x, which should give me 5 more mph in the 2nd gear. Does anyone know off hand that Caterham or anyone that carries a pumpkin with lower final drive ratio with LSD built-in?

 

Do you have a live axle car or dedion? A higher final drive number will mean better acceleration and therefore you will have LESS speed in a certain gear. (EDIT: I think I read what you said wrong..) Nobody will carry a pumpkin with the LSD and R&P built in. Yes, the ring gear is interchangable. I've been looking for a LSD for a long time but cant seem to find one at a reasonable price. I believe a LSD will really transform the car because the rear end is so light.

 

Ride height is adjustable, the shock is not.

 

So you have the bilsteins? Are your swaybars adjustable? Were both the R compounds and FF slicks all the same size? Did you play with tire pressures?

Edited November 23, 2009 by TheDingo8MyBaby

[Boxologist]

Do you have a live axle car or dedion? A higher final drive number will mean better acceleration and therefore you will have LESS speed in a certain gear. Nobody will carry a pumpkin with the LSD and R&P built in. Yes, the ring gear is interchangable. I've been looking for a LSD for a long time but cant seem to find one at a reasonable price. I believe a LSD will really transform the car because the rear end is so light.

 

 

 

So you have the bilsteins? Are your swaybars adjustable? Were both the R compounds and FF slicks all the same size? Did you play with tire pressures?

 

my secondhand knowledge has told me that the LSD would most benficial on an IRS car. even teh deDion setup doesn't allow the LSD to function well on such a light car, experience w/ the car car breaking loose is going more helpful. since thats what i was told, thats worth less than 2 cents.

 

maybe the better final drive is desired so he's not cruising at 3500-4000rpm on the highway? i would have suggested building up the engine for a higher redline to increase top speed in gear.

 

edit: Danny, where was saturday's event? at first I thought u were talking about sunday, but didn't see u listed in teh results.

[TheDingo8MyBaby]

my secondhand knowledge has told me that the LSD would most benficial on an IRS car. even teh deDion setup doesn't allow the LSD to function well on such a light car, experience w/ the car car breaking loose is going more helpful. since thats what i was told, thats worth less than 2 cents.

 

I have a live axle caterham and it suffers mid corner inside rear tire lift. I can't put what little power I have down. I have no doubt a LSD will help. I have another car with a live axle and adding a LSD was probably the best investment yet...

[dannykao]

I have a DeDion rear. The A6's are the same size front and rear, and the slicks I ran was an FF autox tire setup and are staggered.

 

Everything is stock right now and I am getting a wide track setup from Chip as well as height adjustable Bilsteins. I picked up some race springs and a adjustable rear bar. Chip is also helped me to get an intake cam, and George helped me with a skid plate for the oil pan which came in handy in the bumpy lot last Saturday.

 

Most of the parts will be bolted on in the next few weeks. Meanwhile I am finding as many events as I can go before the snow starts.

 

I was in Philly on Sunday to just take pictures and crew for a friend of mine. (And chitchat with Tom, nice seeing you again Tom.) I ran on Saturday with CDC (Capital Driving Club) at Harry Grove Stadium in Frederick - a very small lot but with a few straightaways. Here is a video of my run for your amusement: :jester:

 

 

I was amazed how much speed I can carry in the Steady state (Probably 7-8 mph more than my Evo) and hit the rev limiter that quickly after the exit, hence the question.

 

I did call Chip and will try to verify my final drive ratio. If it's indeed 3.9x then Chip will help me out with the swap and source a LSD. Otherwise my other option might be getting a larger set of wheels and tires and butcher the rear fenders.

 

Oh, I did play with tire pressure and started with 18F/18R and ended up running 18F/15R. I tried to go lower but it got more slippery (Temp was in the high 40s-low 50s). And the entire run should stayed about 3500rpm in the car, at least that's why I was trying to do... :driving:

Edited November 23, 2009 by dannykao

[yellowss7]

Danny, good seeing you again too. Next year will be fun to run with you. Can't wait. As for slick tire pressures, I run my Hoosiers at around 12-12.5 psi cold. When I ran on the track at Barber, I bumped them up to 15-16 cold. It was still pretty chilly on Sunday around 58 or so, and from past experience, it's almost impossible to get or keep any heat into them when it's that cold out.

 

I think that next year, once it warms up in the spring/summer, you are going to see what these cars can really do with new rubber.

 

And if they come up with the next site that they are working on, (a large concrete runway) grip will be incredible.:drool:

 

Tom

[dannykao]

More stupid questions and observations:

 

My "heavy duty" rims I got from Diamond Racing came in today. 13x9 and 13x10 and 4x108mm (4x4.25) with 5" backspacing. Both didn't fit well. The fronts will rub with the fender support in my stock 7, and the rear will rub against the edge of the hub mount. So they are for sale. $35 + shipping per rim and that's half price if anyone wants them. It will fit with 3/4 to 1 inch spacers, I just would rather not to mess with them. Next time I will do a better measuring.

 

Which lead to my stupid question: Anyone ran 13 inch front and 15 inch rear? Hoosier has a 275/35/15 tire that's big enough to give me 65 mph top speed in second gear. (Didn't get a chance to verify the final drive tonight, Chip) 255F/275R sound pretty mean, just wondering if anyone has tried it. It will raise rear ride height by 1 inch.

 

Thanks.

[Boxologist]

Tom was using 13x8 correct? we was able to get 10" wide tyres on, so the A6 or beyond tyres should be mountable.

Did the 13x9 fit the rear?

If u become a member of the UK club, there is a group buy on Compomotives, or if u can get involved w/ that as non-member(i'd get in too) u can get some good 13x8s. i think at 255/275 u'd be overtyred(sic) and then would be playing catch up on the power end.

[yellowss7]

Box, my street tires and wheels were Avon Cr500's 175x55x13 on I believe 6.5 or 7 inch wheels, at the front and Avon Cr500 205x55x13 on 8.5 inch rims on the rear. I just replaced the Avons with the Toyo R888's. Rears are 205x60x13, fronts I think are 175 or 185x60x13. The wheels are the Mike Barnby 3 piece Magnisium wheels that use to come with the R500's before Caterham switched to their 8 or 10 spoke jobbies. Same ones pictured on Craig Chima's car that's being discussed on another thread.

 

The Hoosiers are on 10x13 3 piece Kodiak wheels at all four corners. Don't remember the tire size off the top of my head. If needed I can go take a look at them.

 

Tom

[Boxologist]

i thought the kodiaks were 8" wide as well. were u running a 12" tyre on a 13x10?

[dannykao]

Michael's wheels that he lend me are 13x8 BS4.5 front and 13x9 BS5.5 rear. His A6's are 225/45/13s. The front needs a 5mm spacer to clear the fender support, and the rear is fine except the DeDion hub rubs against the inside of the rim a little.

 

The slicks that folks are running are 22.5x10-13 rear and 20x9.5-13 front. The track width are 9.8" rear and 9.4" front. If you go to the Hoosier's site, they can be mounted on either 8" thru 10" rims. I went ahead and got 13x10's because that's what the Cashmore is running (SCCA Solo Nats Champ), but since I can't swing th money for lighter rims, I think I will stay with 13x8s with 4 inch backspacing for the rear, and 4 or 3.5 inch backspacing for the front. It should fit OK if I go with that.

 

BTW, Hoosier is blowing out their old tires (New but old stock) and you can get 22.5x10x13 R25As for $85 a piece with free shipping. Just go to the Hooiser site under discontinued tires and they are on sale now. Unfortunately they don't have the front size, but I bought quite a few rears to last a couple of years.

[yellowss7]

Danny, if by "Dedion hub", you mean the Dedion "Ear" it it a common problem even with the new Caterham 8-10 spoke wheels. A little light maintenance with an angle grinder on the ear will sort that out easily.

 

Tom

[dannykao]

Thanks Tom! Now I know exactly what you are referring to and I will do that! Thanks for the tip!

[dannykao]

Danny, good seeing you again too. Next year will be fun to run with you.

 

Hi Tom, Chip is sending the wide track kit and shocks to me next week, and I should have some 255/13 A6s for the rear to run with the 255/13 front from Michael D (who generously lend them too me). Do you want to come out and play (co-drive) at the NJMP winter event event next week? It would be great to get your opinion on the differences between the two cars. Thanks!

[sdca7]

I was running Kumho V710 215/50R13's on Panasport 13x7 rims with backspacing of 4.375" on both front and rear with no clearance issues. This was on a '98 Caterham Superlight. It was pretty well balanced.

 

I'm soon getting a more high powered Caterham, and will probably go with the following combination for road racing:

 

CSR wheels. Front 7x13 with 225/45R13 A6's, Rear 9x13 with 255/40R13 A6's.

 

It is tempting to go wider on the front, but I'm guessing that for road racing I don't want to get too far off the original sizes to avoid bump steer and tramlining. It may even be better to just stay with stock tire sizes (I believe 185 front, 205 or 215 rear on the R500). I think wider pays off on autocross courses, but I'm not sure which would be better for road racing.

 

I'll have to check and make sure the CSR rear wheels have proper backspacing, as I'm guessing that with the IRS they may have different clearances than the Dedion.

 

Justin

[yellowss7]

Hi Tom, Do you want to come out and play (co-drive) at the NJMP winter event event next week? It would be great to get your opinion on the differences between the two cars. Thanks!

 

Danny, thanks, that would be fun, but have you checked the weather forcast for Saturday? 40's rain and possible snow. That's Evo conditions not a Seven's.

 

Tom