federal rsr sizing

[KaneDB]

Hi all,

I'm in the process of buying a set of federal rsr tyres for the 300zx. I've read that they come up wider than their marked width. Here's my predicament! I run a 245,40,17 tyre now (hankook) on a 8.5” wheel. The two options I have are:

235,40,17 which will come up somewhere near 245 anyway, but has a lower load rating of 90 in theory 1.2% or 8mm smaller diameter.

255,40,17 I have read is more like a 265, load rating of 94. But I am wary that this might oversize the 8.5” rim. 1.2% larger.

The car weighs something like 1600kg,so I think the 90 load limit would just be OK, but I assume the 94 would also have stronger sidewalls?

Any help would be appreciated

Cheers

[gruffalo]

Many track orientated tyres come up slightly wider than the road equivalent.

If you have the room in the wheel arch just go for the standard sizes, the track tyres are wider because of the shoulder design of the tyre, and would not effect the rim sizing.

[robinandcamera]

Sorry, but I'm not quite sure what you are getting at when you are referring to oversizing the rim and its diameter. Are you worried the larger diameter tyre (from the minimal side wall hight increase when going up in width) will affect the gearing due to the increased size? Is it more the load rating increase?

255/40/17 is perfect for an 8.5 wide rim, see here:
http://www.yokohamatire.com/tires_101/customizing/...
http://www.avonmotorsport.com/road-legal/performan...

I used to have a Honda S2000 and 255/40/17s are often used on them, things like AD08Rs have a load rating of 94 also and the S2000 is a good 300kg lighter than your car and they are fine.

In terms of width. I was curious as I always heard track tyres come up wider so I measured a 225 R888 I had and it was exactly 225mm wide. The tyre was very square with the shoulders being exactly 225, but it wasn't any wider than that. I've not measured any others.

Hope that helps

Edited by robinandcamera on Wednesday 18th March 09:54

Edited by robinandcamera on Wednesday 18th March 09:56

[Darranu]

So to hijack this but what are these tyres like as purely a trackday tyre?

Just can't help noticing how inexpensive they are compared to the rest, even the Nankang NS2R

[Dakkon]

I have just fitted the AD08R to my 350Z and they worked very well on Saturday at Bedford, even with a heavy car such as the 350Z. I was concerned that the weight might overwork the tyre.

Very impressed, and still loads of tread left at the end of the day.

They are about as performance oriented as you can go and still be a 8mm tyre, the Federal RSR is a 5mm semi-slick track day tyre (although still road legal)

[KaneDB]

Sorry for any confusion, I'm not overly worried about the small increase in rolling diameter - tyres fluctuate that much from full tread to worn out anyway.

The main thing I was worried about was going too wide the width on the 8.5 wide wheel if the RSRs came up even wider, but even federal says the 255 is ok on 8.5 - 10" wheels. I'll go for the wider option. I'll post back how I find the tyres when I get them.

[ezi]

I went to these tyres from Toyo T1R's and the sizing is definitely something to be mindful of, in 205/45/16 they actually caused some fouling on the rear arches and I had to remove wheel spaces to rectify the issue!

[4packet]

I've been running (2 sets of the Feds) 235/45/17 on an 8" front and a 255/40/17 on an 8.5" rear. Front looks OK, rears look a little wide for the rim. Next set of Feds in the same size will be fitted to 8.5" and 9.5" rims which I'm expecting to work/look better. Guess I'll know in a couple of weeks if it handles any better with the wider rims....

Car is a V8 RX7 for reference.

[QBee]

I use Federal 595 RSRs on my TVR in preference to Toyo R888s. I find the grip level similar on track, but the Federal gives more warning when close to letting go.

The softer sidewalls of the Federal mean I run my dampers stiffer. But I can also use them as road tyres, which is a bonus.

I have just popped outside and measured the tyres - my 215/45 17s are.........wait for it........215mm wide.
In my experience it is the Toyos that are 10mm or so wider than advertised.

[sydown]

I found the feds came up slightly wider but with a 1600 kg car overheated within a couple of laps at bedford in the dry, have found the ns2-r to be better on thermal consistency!

[QBee]

sydown said:

I found the feds came up slightly wider but with a 1600 kg car overheated within a couple of laps at bedford in the dry, have found the ns2-r to be better on thermal consistency!

That's a useful comment. On an 1100 kg TVR they just get nicely to temperature.