Choosing between rims for a track car

[NitroDann]

If "lowest offset is best" because "wider track", we would all have 3m wide cars with -75 offset wheels.

The suspension, steering and hubs are designed with an offset in mind, the further you go from this the bigger compromise you are making, other wise 6ULs would be 0 offset or some wanker rubbish, but they are +36, which is the offset needed to fit 8" wide rims on a stock but guard rolled car. Thats the highest offset they could manage. If not they would just go even lower, but then the car would handle rubbish.

Dann

[rascal]

The suspension, steering and hubs are designed with an offset in mind, the further you go from this the bigger compromise you are making, other wise 6ULs would be 0 offset or some wanker rubbish, but they are +36, which is the offset needed to fit 8" wide rims on a stock but guard rolled car. Thats the highest offset they could manage. If not they would just go even lower, but then the car would handle rubbish.

Dann

I'd suggest 6UL are +36 as this is the size that appeals to the largest market, meaning more sales. If they were lower offset to suit the racers but needed guard work to fit, then Emilio would lose all the customers who don't want to modify guards.

I disagree on your generalization that lower offset would handle rubbish. Depending on your usage, some compromises are worth it to make gains in other areas.

Widening the track with lower offset rims will improve cornering ability, as it decreases weight transfer, allowing better use of the tyres available grip.

So for someone far more interested in cornering speed than your usual daily driver, lower offset rims are preferable.

[Boyracer]

Don't waste your time getting S spec Tyres, it's a track car and it's all about going fast, you should get R specs... They will be heaps better than road Tyres and way better if it rains.

[david_syd_au]

Don't waste your time getting S spec Tyres, it's a track car and it's all about going fast, you should get R specs... They will be heaps better than road Tyres and way better if it rains.

In theory that is true, however I wonder if as newbies we need the extra grip, which would mean we are potentially going faster when we stuff up, and also the additional complexity of tyre heat management.

Our car is effectively stock, just with the interior stripped out and a roll cage added, but will be running in class 9 with much more highly developed race cars. I would like to run it in a similar spec to the clubman class cars even though we won't be in that class, to allow us to benchmark ourselves against them.

So, thanks for your thoughts, but for now I will stick with using the S-spec tyres.

In a years time, we'll see :-)

[Boyracer]

Honestly you will regret it running S spec, get yourself a set of R888 Toyos, they are not as hard core as a lot of the other semi slicks and will work a lot better than a road tyre.

[Sailor]

S Specs on a lightweight track car are just rubbish.
You need a tyre that will warm up fast with the light loadings and generate some grip.

Ask ANY of the guys that did Natmeet at Wakefield on S specs compared to their normal R spec tyres.
There will be a unanimous decision that the S Spec though good and recording times far better than many expected, just didn't have that extra measure of security.
I'll say it again.
The R spec will give you the extra safety margin in that ooops moment...might just be the half metre you need to stay off the armco, tyre barriers or the guy who spun in front of you.

AND they're as cheap, or is that expensive ? , as a good S spec

[Guran]

Jeez, that's a bit harsh Rob. S specs are bloody good for what they are: about a second quicker than normal street tyres (at Wakefield), cheaper than R specs and don't need to be brought up to temperature before they stick. Excellent in the wet too - which will be very handy this weekend! So I can understand David's decision. On the other hand, if it were me in his position, I'd still be going with R888s and just jump in the deep end. It's a race car afterall.

[Sailor]

Don't get me wrong!
By "rubbish" I meant a waste of a good car not that S specs are rubbish
I was thoroughly impressed with my Toyo T1Sports, I was just coming to grips (or lack of) with them when I went for the brownie points.

Thing is, this IS a race car as you say Guran.
It will be trailered to/from meetings so a good set of R specs like the R888 will last for ages....maybe even too long like mine.
Hell you could even go for some of the cheaper stickier R specs just because they wont be dríven on the road!

[david_syd_au]

Thanks all for you insightful input.

For now I am sticking with the S-specs, for a bunch of reasons that I won't re-hash.

Next year, may switch to R-specs for the track, and relegate the S-specs to motorkhanas. With a few more track days done, I will be in a better position to make use of faster tyres.

Hope to catch up with a few of you at Wakefield on Monday. Got to remember to bring umbrella, raincoat, gumboots etc :-)

[deviant]

I know minds are made up and money spent but in a stiff caged car with circuit alignment / suspension and circuit spec brakes those road tyres can be destroyed in a very short period of time....like 20 laps period of time. My first turbo NA with all the fruit made its almost brand new Toyo R1R tyres bald in about 15 competitive laps, they are not that much cheaper than R888's either.

It is easy to over drive when you feel like the car has so much more to give and when you are strapped in to a decent seat, you wont even feel like you are moving on road tyres so will try and drive harder.

[david_syd_au]

I know minds are made up and money spent but in a stiff caged car with circuit alignment /

Yes

suspension

Stock 100k km springs and shocks

and circuit spec brakes

All NB8A original with unknown quality brake pads

those road tyres can be destroyed in a very short period of time....like 20 laps period of time.

Given the weather forecast for Wakefield this coming Monday, tyre destroying will have to wait :-)

My first turbo NA with all the fruit made its almost brand new Toyo R1R tyres bald in about 15 competitive laps, they are not that much cheaper than R888's either.
It is easy to over drive when you feel like the car has so much more to give and when you are strapped in to a decent seat, you wont even feel like you are moving on road tyres so will try and drive harder.

All part of the learning experience. Thanks for the warning.

[david_syd_au]

A brief postscript to wrap up this thread.

The MX5 club trackday was held yesterday (Mon 4/6/12) at Wakefield Park, and despite all the predictions for wet weather it was actually a dry day, with some sunshine in the morning then clouding over and becoming cooler during the afternoon.

The Kuhmo KU36s performed well, having more grip than any tyre I have used previously, as they should being my first S-spec tyres.

This was the track car's first outing, so the day was more about trying out the car and learning as a driver, rather than pushing any limits, demonstrated by the fact that I had no off track excursions for the day.

The tyres had a mostly gentle and progressive loss of grip when pushed a bit, and I am happy that they will help provide a good and safe platform for my son and daughter on their first track days.

Next year, when we all have a little more experience we will look at replacing them with something better.
Thanks to all for the advice given last week

[project.r.racing]

If you said you were getting KU36s somewhere in this thread. You might have gotten a different response from alot of people. The KU36s sit in that small grey area between R-spec and S-spec tyres.

[david_syd_au]

If you said you were getting KU36s somewhere in this thread. You might have gotten a different response from alot of people. The KU36s sit in that small grey area between R-spec and S-spec tyres.

Sorry :-)

When I started this thread I didn't know which tyres I would be getting, but was trying to decide which set of rims to use for track work.

Anyway, it all worked out well, and I am sorry for any unnecessary aggravation.

[Suspense]

If you said you were getting KU36s somewhere in this thread. You might have gotten a different response from alot of people. The KU36s sit in that small grey area between R-spec and S-spec tyres.

In between s spec and r spec? I thought the KU36 were at the lower end of the scale of s specs.

David, what did you end up paying for the KU36? I was ringing around a whole lot of places this week to find a set at a reasonable price but the few places that had them or could get them in we're quie expensive. In the end I went with paying a small amount more to get star specs from the US.