Tires and Seats for a Seven

[RogerL]

I am building a kit from the UK starting end of this month. What is your recommendation on tires for track use but still legal for the street?
I will be using 13 inch wheels. Is 8' wide wheels recommended or is 7" OK ?

Seat choice is limited because of the narrow cockpit. I am looking for
a roadrace style seat. I don't know what brand of seat Caterham uses.

[psz.]

Avon ACB10's seem to be the tire of choice for "spirited" street driving as well as excellent dry track use.

As far as seats go, Caterham uses seats made by Tillet. They have a new model coming soon that is lower in price than the existing models. You can find more at: http://www.tillett.co.uk/

regards,
PSz.

[venom7]

Personally I find the Avons to tram too much. The Hoosiers I had before were a much better tire. I'm happy with the Avons for the price but if I was to buy new tires again it would be Hoosiers then 032r's.
Thats my 2 cents.

[Roll a 7]

I have been using Kumho 13" tires. Better than ACB10s and much less expensive.

[JohnCh]

I have MOG seats in my Westfield and am happy with them. I recently tried the Tillets in a Caterham and didn't notice much difference in size or comfort. However, the carpet-like material Tillet installs on the side supports was a nice touch and helped keep me in place a little better.

-John

[Rich H]

I am building a kit from the UK starting end of this month. What is your recommendation on tires for track use but still legal for the street?
I will be using 13 inch wheels. Is 8' wide wheels recommended or is 7" OK ?

Seat choice is limited because of the narrow cockpit. I am looking for
a roadrace style seat. I don't know what brand of seat Caterham uses.

An Avon ACB10 (a sticky bias-ply tire optimized for Caterham) together with the Barnby wheel that Caterham used to fit standard on Superlight variants, weighs around 20 lbs. Anything else road-legal will be heavier, but cheaper. And a radial tire may feel better to you on the road.

The Avon CR500 is a radial optimized for Caterham, but weighs a couple of pounds more than the ACB10. That may not seem like much, but I find 2 lbs. per corner is quite noticeable on my Superlight.

I think that all of Caterham's speed record setting has been done on Avons.

[Elv15]

Tires

I run 13" minilites with Yokohama A032 tires - 6" fronts and 8" rears. Both the rims and the A032's are heavy. I will be seroiusly thinking of switching to the ACB10's after these are worn out.

I would venture that tramlining has a lot to do with how your suspension is setup...the method of tire constrution is only one factor. My car tramlines a bit with these radial tires, but I am running approx ~0' toe.

Rich, the Barnby wheels are great, however, I'd be curious to find out the difference between the Barnby wheels (in both weight and price) and some of the more local offerings, like Kodiak.

[Roll a 7]

Many of us have two sets of wheels and tires and just switch 'em depending upon the application. Some over the edge nutcases, like me, have three sets mounted.

The available selection of 13" tires is very limited in the USA.

Barnby wheels are ridiculously light!!

[Rich H]

I run 13" minilites with Yokohama A032 tires - 6" fronts and 8" rears. Both the rims and the A032's are heavy. I will be seroiusly thinking of switching to the ACB10's after these are worn out.

I would venture that tramlining has a lot to do with how your suspension is setup...the method of tire constrution is only one factor. My car tramlines a bit with these radial tires, but I am running approx ~0' toe.

Rich, the Barnby wheels are great, however, I'd be curious to find out the difference between the Barnby wheels (in both weight and price) and some of the more local offerings, like Kodiak.

Tom, I don't know how Barnby compares to Kodiak. I have CR500s and ACB10s mounted on Barnbys and can weigh those if anyone has the same sizes mounted on Kodiaks to compare. I've come to distrust published wheel/tire weights and like to see the numbers on my own scales.

Good point about alignment, especially toe. Switching from CR500s to ACB10s on my car does, however, increase tramlining. But the tramlining is more steering info, not bad unless one just doesn't like the feel.

[soareyes]

Can someone explain exactly what "tramlining" is? I don't think I have it, but just curious. A description of "bump steer" would be appreciated too!
Thanks,
Stan

[slomove]

As for "Tramlining" I feel this very much when changing from the 15" Bridgestone road tires (radials) to the 13" ACB10. Normally I don't drive them on the road, but when I do the difference is:

I can let the steering wheel go with the radials even when the road is somewhat uneven. The car just goes straight. With theACB 10 I need to hold on to the steering wheel and give constant correction. This is especially bad when the road has some truck furrows or is crowned.

This does not matter on the track, though...pretty flat and you are anyway working the steering wheel :)

Don't know much about bump steer except it is a sign of bad steering geometry.

Gert

P.S. I run both tires with about 1/2 degree negative camber as a compromise.

[JohnCh]

Tom,

I sent Kodiak a mail a while back asking the weight range for a 13 x 7 FX wheel and was told that they usually come in at 6.5-9 lb depending on offset. I don't believe Caterhams use a lot of offset (15mm?), so the weight is probably on the heavier end of that spectrum.

-John

[moosetestbestanden]

In my echats w/ CC when I went thru the CR500 to ACB10 switch I was told to leave the front end pretty much alone. I did that and while I experience some understeer in tight corners w/ the CR500s on the street I don't really care because it happens at go-to-jail type of speeds and I just don't go there anymore. The CR500 are significantly better for the road otherwise.

It's ACB10s for the track. Note that CC sells a different DeDion ear for the rears to adjust the camber. The switch takes a couple of hours to do.

[Elv15]

Bump Steer

Soareyes,

Bump steer is when one or both of the front wheels is turned by the action of the front suspension. Put another way, when your front wheel hits a bump the track rod will follow an arc and effectivly shorten, causing it to "twitch" the wheel.

BTW, there is a nice article on bump steer in the June edition of Low Flying.

John,

Thanks for the info! Anybody know what the Barnby wheels weigh?

[Rich H]

Soareyes,

Bump steer is when one or both of the front wheels is turned by the action of the front suspension. Put another way, when your front wheel hits a bump the track rod will follow an arc and effectivly shorten, causing it to "twitch" the wheel.

BTW, there is a nice article on bump steer in the June edition of Low Flying.

John,

Thanks for the info! Anybody know what the Barnby wheels weigh?

Haven't seen weights published by Barnby himself, but writers on BlatChat say different things, ranging from 2.6 kg to 3.2 kg for a 13 x 6.5. As I said earlier, its best to compare weights directly on one's own scale.