13" Wheel sizes and Offset

[Ross_328i_sport]

I tried completing a search and whilst finding some helpful information I still have a few questions hence the post.

I have recently bought a Caterham SV running Duratech engine and am looking to change the wheels to Compomotive cxr's running R888 tyres.

Front tyres - 185/60/13
Rear tyres - 205/60/13

Whilst doing some research on what size rims are the best I came across the guidelines recommended by Toyo.

http://www.racetire.com/products/toyo_r888.htm

Where 5.5" fronts and 6" rears are the best recommendation for the tyres above. However I have noticed that most owners run 6" fronts and up to 8" rears. Is there a reason for running the wider wheels?

Before finding the above information I was set to order 6" fronts and 8.5" rears with an Et24 offset which is the offset and sizes supplied on the superlight. Would the offset be different for a SV type car?

Appreciate any help as my heads beginning to hurt!

Ross

[snapper seven]

I've never heard of any Seven running 5.5" front tyres but could be wrong. As you say, for the more powerful Sevens you will find most people run 6" fr and 8 or 8.5 rr and the reason mainly is simply to give more grip.

Some people run 6" all round but with 185s on the fr and 205 on the rr to offer more grip too.
205s are tight on 8.5 rims but fit fine. Just means the tyre offers no protection for the wheel rim.

It sounds as though you are ordering the right sizes for the Comp CXR wheels. There was a bulk buy on Blatchat a while back for these wheels so there would probably be plenty of info on that thread.

ETA - Just found it http://www.blatchat.com/t.asp?id=199713

Cheers
SS

Edited by snapper seven on Wednesday 2nd May 13:17

[James.S]

Don't know the reasons for the Compo's but weigh a set first, ime they are much heavier than they say. Very strong wheels though. On that piont though do not think you an beat CC's eightspoke - cool wheel, strong and reasonable money. Made by KN in Brum.

Forget the 888's stick with CR500's or ZZR's. So many people overtire Caterhams.

J

[sam919]

I have just weighed and checked offsets:

1370 CXR = 5.40 kg based on the average of two at 5.38 and 5.42kg. Offset ET20.

1385 CXR = 5.86 based on one as couldnt find the other. Offset ET20.

Tyres, R888 are a good tyre, probably better on 8" rears for the 205, as you pointed out. Kumhos in medium are a good tyre, stiff side walls but good grip unless in the wet. Never tried the ZZR's but heard some good reports. I would go for the R888 in GG/ Medium compound, good all rounder.

CR500 = around 500 quid and R888 £350.

Set of CXRs approx 500 made to order + R888 = £850

Anthracite 6 + 8 x 13 plus CR500 over a grand if you can get hold of them.

A little weight difference but nothing to worry about, save yourself £150 for a track day. The 205 + 185 is a good combo and you can still slide it about or drive like a vicar.

Edited by sam919 on Wednesday 2nd May 14:41

[James.S]

Think Kuhmos and 888's are quite a bit heavier than 500's nad both are rubbish in the wet - so you need another set of tyres for the damp or stay in the garage, so don't agree with the cost point.

Also, and much more importantly they make the car handle horribly - imo the tyres are too heavy for the front and carry too much grip.- oh and mediums are too soft for anything other than qauli

You can also sell used 8 spokes quicker than almost anything bar used half doors!!

J

[sam919]

Yes they are around 1.5 kg but the R888 i found pretty good in the wet, the Kumhos+R888 you can put the psi up and open the tread and they are a lot better although not the best. If the Kumho route was taken a 215 and 175 are a good combo for 6/7 front and 8 rear. The medium is the tyre of choice in Kumho, hards are rock solid, i have done a 40 min Mag 7 race on medium (if its the Kumho we are on about) and they were fine with R500 power, and with a little tyre managment.

I havent found the car to handle horribly i think when there on there pretty decent, the 215 kumho as fronts maybe a little heavy but when you have some proper power you need the front end grip otherwise the car just gets understeer from the power/ grip of the back wheels, more grip/ rears needed to get the power down.

If there that good why would you want to sell them?!

Its down to individual driving style, and not being a victim of caterham marketing? .

[James.S]

lol

[Ross_328i_sport]

Thanks for the advice.

The reason for compomotive's is overall balance between weight, price, strength and aesthetics.

The reason for R888's is that I already have them from a previous car however in the future will probably change to Cr500's.

Looking at the compomotive site I personally prefer the designs of 6" (CXR-1361) Max (ET22) and 8" (CXR-1380) Max (ET19).

Would you see any issue using the above design and would you use the same offset front to rear i.e. ET19?

Using this would increase the track if my understanding is correct therefore would this affect performance?

[sam919]

As above the set i have for 7 and 8.5 both use the same offset of ET20. I use 8s and 10s for larger tyres and these are ET-8 and ET-7, so i dont think you'll be far off '1mm' by using ET19 on both front and rear.

The track, someone please correct me if wrong but a wider track gives better low speed cornering and narrow track is better for high speed cornering with relation to track without any other set-up charachteristics taken into account. (where's Sam_68 when you need him?!)

[TomCat1]

Sorry to dig up an old thread but this is the closest thing I can find .

I have a 1.8 kseries 2003 roadsport, it has a big brake upgrade, it's currently got 13 x 6" all round et16, this sounds a funny offset I've not seen many other people have this offset.

Would r500 wheels for with an off set of et 24 all round running 6" on the front and 8" on the back fit?

[jackh707]

Agreed on 888s being ok in the wet. If its not standing water, wacky them up to 20psi. Once warm, loads of grip.