Caterham ride height

[supersportsp]

Question for Caterham owners or folks knowledgeable about this in general.

 

There seems to be a pretty good deal of variance in ride height in the various Caterham pics I have seen. My car, especially at the rear seems to be low. Perhaps, due to my 200 lbs butt, but even at rest it sits much lower than other cars I see.

 

For example. YellowSS7's car. Granted, he has 13" wheels and what seem to be relatively low profile tires, but look at the difference in wheel centerline on his car compared to mine below:

 

http://usa7s.com/vb/attachment.php?attachmentid=2710&stc=1&d=1296263517

 

http://img.photobucket.com/albums/v715/tgodbout/IMG_6498.jpg

 

I am running 15" wheels with 195/50/15 tires.

 

Some more variances:

 

http://www.google.com/url?source=imgres&ct=img&q=http://www.seriouswheels.com/pics-2007/2007-Caterham-Seven-Roadsport-150-Side-1024x768.jpg&sa=X&ei=SQBLTd2WFpD6swP1u_ybCg&ved=0CAQQ8wc&usg=AFQjCNFf2yrYlt6XU6PspPj_bSNIr6z4lA

 

http://www.google.com/url?source=imgres&ct=img&q=http://www.sbeuro.com/domhost/locostprime/caterham-1-g.jpg&sa=X&ei=6gBLTdW1DofAsAOdxNyUCg&ved=0CAQQ8wc4SQ&usg=AFQjCNGh59Iw0kedusEJhalfIQWRhO42ug

 

So, why the variance? Since it seems to be the newer, more track focused cars that have a raised rear ride height, I thought it might have something to do with perhaps reducing understeer? But then I saw some race cars that are lower all around like the car above.

 

Who can explain?

[bball7754]

Believe the "standard" setup is to have 10-15mm of rake, with the rear higher. Research on Blatchat indicates that the handling can be somewhat evil without the rake.

 

Steve

[scannon]

Believe the "standard" setup is to have 10-15mm of rake, with the rear higher. Research on Blatchat indicates that the handling can be somewhat evil without the rake.

 

Steve

That's what Nathan Down did when he did the corner weighting and alignment on my SV.

[blubarisax]

I don't know about you guys, but I like the grinding sound of the seat bolts hitting the pavement!

 

Seriously, mine is about 3 1/2 inches with me in the car. After my first flat floor setup the ride height was less than 3 inches, not too good for New Jersey roads. Now I watch for high spots in the road and try to ride over them with the wheels.

[yellowss7]

That picture of my car is from the first time it rolled out the the garage. It had not been cornerweighted at that time. Although I did set it up using the 15mm rake recommendatiion in the build manual. I think I had 75mm clearance under the sump. If you think those tires are low profile, (they are 175 55 13 front and 205 55 13 rear) then you should see it on the 13 inch Hoosier slicks, They are REALLY low profile. Luckily most tracks are pretty smooth.

 

Tom

[supersportsp]

What is purpose of the rake? I am assuming it is to put more weight on the front wheels to increase turn-in grip?

 

As I didn't build my car, how does the manual recommend to measure the rake? Where do you measure from? With you in the car? How much fuel in the tank etc.?

[yellowss7]

From memory, I believe you measure the rear from just forward of the rear arch, and from the front under the motor mounting bolts. I'll try and dig up my build manual and check that.

 

Build manual doesn't give much direction. BlatChat archives state measure under the sideskin, just behind the front wheel and at the rear under the side skin in front of the rear wheel.

 

15 mm is a starting point. Increasing rake tends to increase oversteer. Ie, the back gets lighter, Less rake usually results in more understeer.

 

Measure as you would drive the car, Fuel level, passengers etc. Might use half a tank as a median point.

 

Tom

Edited February 3, 2011 by yellowss7

[supersportsp]

From memory, I believe you measure the rear from just forward of the rear arch, and from the front under the motor mounting bolts. I'll try and dig up my build manual and check that.

 

Build manual doesn't give much direction. BlatChat archives state measure under the sideskin, just behind the front wheel and at the rear under the side skin in front of the rear wheel.

 

15 mm is a starting point. Increasing rake tends to increase oversteer. Ie, the back gets lighter, Less rake usually results in more understeer.

 

Measure as you would drive the car, Fuel level, passengers etc. Might use half a tank as a median point.

 

Tom

 

Hmm. I measured from where the frame flattens totally (right behind the front axle line) for the front, and in the back on the frame bottom right in front of the rear wheels.

 

Front: 133.35mm

Rear: 139.7mm

Delta: 6.35mm

 

Add my girthy self and I wouldn't be surprised if I had any rake at all. Certainly well outside of the guidance range as you guys are saying here. Seems like 1/2" would be smack in the middle.

 

YellowSS7, I have you beat on sump clearance. I have a whopping 69mm to play with.

[yellowss7]

 

YellowSS7, I have you beat on sump clearance. I have a whopping 69mm to play with.

 

Yeah, I suspect that we both have to becareful not to run over any squirrels or we could get High Centered by them. :smilielol5:

 

Tom

[JohnCh]

Here are the directions from the Caterham Assembly Manual:

 

29.1 Start by adjusting the front dampers to achieve a minimum distance of 150 mm (this can be increased for road use to a maximum of 190 mm) between the ground and the bottom of the lower chassis rail, where the rear leg of the front lower wishbone exits the side of the car. This measurement should be the same on both sides with the car loaded.

 

29.2 Now adjust the rear dampers in the same manner to achieve a height 15 mm higher than the front, measured to the underside of the lower chassis rail immediately in front of the 'A' frame mounting point.

 

NOTE

Adjusting the rear may have an effect on the front therefore it is good practice to check between front and rear several times during adjustment.

 

-John

[Kitcat]

Why not drive it first, see how it handles, then dial in/out rake if its not right? I have never measured my rake, but the car handles perfectly, balance is excellent, etc. I think I have abt 3 1/2" ground clearance below the oil sump.

[supersportsp]

Why not drive it first, see how it handles, then dial in/out rake if its not right?

 

I have had the car 1.5 years and have had it on the track several times in its current guise. It understeers on turn-in.

 

I have never measured my rake, but the car handles perfectly, balance is excellent, etc.

 

I understand the if it ain't broke don't fix it approach, but how do you know it wouldn't handle better if you didn't tweak it some.

[Kitcat]

I didn't realize it had been driven. Never mind:).

 

You can fix under-steer by playing w/air pressure sometimes, or adding more anti-roll bar in the back, wh/makes the front stick better. Or by adjusting rake it seems.

 

Let us know if the tweaks help and if you like the (hopefully) more neutral handling.

[supersportsp]

I didn't realize it had been driven. Never mind:).

 

You can fix under-steer by playing w/air pressure sometimes, or adding more anti-roll bar in the back, wh/makes the front stick better. Or by adjusting rake it seems.

 

Let us know if the tweaks help and if you like the (hopefully) more neutral handling.

 

Adjusting the rake will probably be the last thing I do. I am putting on the wide-track kit, the larger front roll bar and debating on a new spring/dampener solution.

 

In fact, I can't even adjust the rake right now because I don't have adjustable collars for the springs yet.

 

I will have some built in rake from my new track wheels that I just bought from Karl.

 

I don't run a rear sway at this time. Might add that as well.

[Kitcat]

The "rule" for tweaking handling is just make one change at a time. Hopefully that will let you isolate the result. My wild guess is that the wide track alone will resolve things. It wld be interesting to put Karl's wheels on before changing anything else to see effect. Of course if car is torn apart, house surrounded by snow etc, that may not be feasible.

[Ian7]

Adjusting the rake will probably be the last thing I do. I am putting on the wide-track kit, the larger front roll bar and debating on a new spring/dampener solution.

 

In fact, I can't even adjust the rake right now because I don't have adjustable collars for the springs yet.

 

I will have some built in rake from my new track wheels that I just bought from Karl.

 

I don't run a rear sway at this time. Might add that as well.

 

Few comments at both this post and #13 above it:

1. changing to "track wheels" won't alter the rake unless you mismatch tire or rim diameter front to back; all it does is raise or lower the car overall.

2. changing the rake is the FIRST thing you should do, not the last. I noted you can't yet, but don't mess with the car much until you can. Your turn-in understeer is a classic symptom of too little rake.

3. adding rear anti roll bar stiffness will be a band-aid fix to this problem, but the first rule of chassis tuning is to fix the end of the car that is defficient. In this case, you are reducing rear grip with the stiffer rear bar to get a more neutral balance, but your overall cornering grip is less, to the detriment of max cornering potential.

4. overinflating the rear tires is another common band-aid to understeer, but same overall reduced grip comments apply.

Edited February 4, 2011 by Ian7
typo

[blubarisax]

The Avon ZZR front tires tires (185/55-13) are 1.15 inches smaller in diameter than the rears (215/55-13). If you are currently running on the same sized tires front and back, then you should effectively lower the front end 1/2 inch.

[supersportsp]

The Avon ZZR front tires tires (185/55-13) are 1.15 inches smaller in diameter than the rears (215/55-13). If you are currently running on the same sized tires front and back, then you should effectively lower the front end 1/2 inch.

 

And hence the auto-rake comment. And my desperate need to get adjustable spring collars it would appear. I can't even imagine how low my oil pan is going to be with the new fronts. According to specs on the Toyo and Avon sites, I will be going from 22.7" (T1Rs) to 20.85" (ZZRs). Yikes!

 

I say I am not going to mess with rake until very last because that is going to be the last step in my process. I am not doing anything until I get my wide-track set-up on, new springs etc. No sense setting up the rake, then changing everything. With all the new stuff on, I will corner balance it and set a baseline rake.

 

I am not trying to solve a particular ill so to speak, I am doing some general upgrades to the car's suspension to give me a better baseline to work from.

Edited February 5, 2011 by supersportsp

[MichaelD]

Don't forget that all corner weighting should be done with your weight in the drivers seat. You are wasting your time otherwise. 5 gal buckets of gravel stacked will do the job, if you don't happen to have a bunch of weights sitting around.

[Ian7]

Don't forget that all corner weighting should be done with your weight in the drivers seat. You are wasting your time otherwise. 5 gal buckets of gravel stacked will do the job, if you don't happen to have a bunch of weights sitting around.

 

... or, give a buddy a beer and a magazine and put his butt in your seat for the half-hour this takes :-)