F1technical.net

Are these front (narrow) tyres on rear (wide) rims?

I remember seeing once Sauber using front wheels on rear axle during qualifying in Monza on dry (less drag attempt) but this Renault combo is strange.

BTW, notice the gills on R26 - no more winter temperatures.







Same thing on Mclaren

I think you're right, the tires on the rear rim look the same width as the front ones and don't appear to fit! A very good observation.

Yes, they have the same number of grooves front and rear. Very interesting. I'd love an explanation, but I can't think of anything. It's illegal during a race isn't it?

I don`t think it would be illegal.

The 4 tyres are made of the same compound and there is only a max. width limitation, not minimum.

To the guest, the tyres will have the same number of grooves (4) no matter how wide or narrow the tyre. The FIA stipulate 4 grooves for every tyre.

I can't really think why they might try this. Clearly there would be less aerodynamic and road drag. However, narrower tyres wear faster for the same compound. Perhaps the teams were investigating the car's ability to put heat into the rear tyres? It looks likely to be a Michelin-driven idea though as both their top teams are testing the setup.

Strange.

What intrigues me is that they tested dry tires in that strange combination on deliberately wetted circuit. Wetting isn't strange but testing dry tyres on wet circuit is. I guess that they tried to test if running narow tyres on wide rear rims would be better than running wide intermediates (less aquaplanning and less aero drag). Perhaps some other day they'll test narrow intermediates and wets in same way?

manchild wrote: What intrigues me is that they tested dry tires in that strange combination on deliberately wetted circuit. Wetting isn't strange but testing dry tyres on wet circuit is

These aren’t dry tyres, they have 5 grooves and not 4, they are definitively wet tyres. And to use thinner tyres on the wet makes sense, in fact wet tyres are usually a bit thinner than the dry ones, not as much as these new rear Michelin though.
The rear tyres look very similar to the front one. The rim is certainly wider though because, according to the rules, the minimum width for the rear wheel has to be more than maximum width of the front one.

12.4 Wheel dimensions :
12.4.1 Complete wheel width must lie between 305 and 355mm when fitted to the front of the car and between 365 and 380mm when fitted to the rear.
12.4.2 Complete wheel diameter must not exceed 660mm when fitted with dry-weather tyres or 670mm when fitted with wet-weather tyres.

Ok, so I didn't count the grooves

FIA regs mention max width od whole wheel (tyre and rim) so, there would be no point for them to stick to wider rim that would deformate tyre so much. I'm cartain that those are not "new rear tyres" but the ones identical to front ones tested in that way for some reason known only to Michelin.

manchild wrote: FIA regs mention max width od whole wheel (tyre and rim) so, there would be no point for them to stick to wider rim that would deformate tyre so much.

The point is, the one I was trying to make, first of all to meet FIA rules. As long as the rim guarantees the minimum width required by rules (365 mm, that is more than the maximum allowed width for front, 355 mm), then you can do whatever you like, within practical limits obviously, with the tyre width.
This means that to fit front tyres with front rim at the rear wouldn’t be allowed by rules but to fit front tyres on rear rims at the rear is. (besides, even discounting the rules, a front rim fitted at the rear would also lead to a reduced wheel track)
Then if these tyres at the rear are actually front tyres or just similar, in tread dimensions and pattern, but with redesigned sidewall to work without problems with a wider rim, I can’t know for sure; the latter makes more sense.

But front tyres on narrow (front) rims are wider than the rim, same goes for rear tyres on wide (rear) rims. So, the teams are meeting FIA rules with width of pneumatic - not by width of rim. That is why I say that if Michelin wanted such narrow tyres on rear for real they'd put them on narrower rims and meet FIA regulations by width of sidewalls and save some weight on rims too.

Those tyres are quite bizzare, usually you can see a tread pattern on the tyres if they are wets or intermediates...but these just look like dry tyres with 5 grooves, i know they're not, but they look like that.

I wonder if this is a new concept intermediate tyre?

Oh btw...400 posts for me, woohoo. hehe, sorry for the OT.