Tire size's could do with advice

[daviesbike]

i am currently running 245 45 18 bridgestone potenza

i would like a better ride from the car can i fit 245 55 18 or maybe 245 50 18 to the rs6 wheels i currently have
what will the side affects be ?
how much will it affect the speedo how many mph will it be out + or -

the car is tracking all over the place as in it feels like a real effort at times to steer the car because it seems to want to follow all the ruts in the road and chase the white lines

also how would it be with the firm ish ride set up i have at the moment

many thanks +++

[HPsauce]

The tyre calculator I use http://www.tyres-pneus-online.co.uk/tyre-equivalence-advice.html
says 7.2% difference, i.e. speedo seriously underrepresents your speed.

There may also be wheel arch clearance issues.

[daviesbike]

Hmmm is there no way to recode the ecu to a new profile or is it all to do with abs sensors ect ..?

[daviesbike]

so if i Go to a 245 50 18 its only 3.4% out with speed of 62 mph its actual at 64 i could live with that if it makes a difference to the quality of the ride

[ainarssems]

There is a lot of difference in ride quality depending on manufacturer and load index. Higher load index = stiffer side-wall = harder ride.

I just changed from Avon ZZ3 to Michelin Primacy Alpin on A6 both with the same load index of 93 ( minimum is 91 for that car) and it feels like different suspension- a lot softer on bumps and potholes but the same or better stability in the corners.

As for the speedo -on some cars you can calibrate it, have not looked it up for A8 and all/most cars show higher speed on speedo then actual with standard tyres, check yourself comparing to SatNav.

Also you need to inform insurance company if you changing to non standard tyre size and it may attract additional premium.

the car is tracking all over the place as in it feels like a real effort at times to steer the car because it seems to want to follow all the ruts in the road and chase the white lines

You might want to check suspension bushes and wheel alignment for this- full alignment not just tracking.

[daviesbike]

when i say its tracking i mean its following the pattern in the road and im not sure if this is because of the lower profile of tyre to what was on there before but when it had a 55 profile on the 17" winter wheels it never did that, but if im buying tires i would prefer to spend on the 18" wheels rather than 17"s but at the same time fix the ride quality,

would it have an affect with this if the tracking was out at all ? or if the alignment was out ?

also would an increase from a 45 to a 50 profile be sufficient to feel a difference on the road comfort wise ?

[sarg]

any car with low profile hard-sidewall tyres is going to tramline like that, run-flats on BMWs are probably the worst for this.

I don't think it will be tracking or alignment, it's just a characteristic of the tyre/suspension set-up the harder you go

[PsYcHe]

I've found my D3 worse for it than my D2, mostly down to the 19's vs 18's of the D2.

[daviesbike]

tramline !! thats the word i was looking for thanks, so do you think its worth a try with the 50 instead of the 45 profile then ?is it worth it

[Architex_mA8tey]

I've found my D3 worse for it than my D2, mostly down to the 19's vs 18's of the D2.

You wanna try my Kahn wheels on 25 and 30 profiles haha they love tramlining and on top of that the width and the staggered set up makes them want to stay in straight lines on bends more. Having said that I try not to get up too much speed for fear of hitting potholes. . . . :(

[christhompson]

When I bought mine it was shod with 225x40x18 and the ride was hard and it tramlined. I changed to 225x45x18 which was an improvement but I suffered a lot of sidewall damage [here in rural France if you have to share the road you often have to run onto the grass verge and if the tarmac surface is damaged at all when you rejoin the damage rips out the inner tyre wall!].

CTL recommended
May I suggest you keep your 18s but run oversize tyres. Try 245/50-18 or 225/55-18 which should improve the ride. Your speedo will under read by 2.5 mph but as it is optimistic any way you will probably find if you compare it with your satnav speed readout you'll be doing 75 or 6 by the time your speedo shows 70.

and so I am asking the local garage to source a set of second hand tyres 225x55x18. I have asked for an almost knackered set [1000km remaining?] and if I like the feel I'll buy a new set

[HPsauce]

Sounds like a good solution.

My little car (Focus Zetec) has hard-ish suspension and normally 195/55 (R15) tyres but for winter has 195/60's which are definitely softer despite the minor difference of just a few mm.
The speedo is now more accurate but still underreads slightly.
(next spring it's going up a rim size to 205/50/16 so I'll see what that does to the handling)

I haven't done much driving in the S8 with the winter setup yet, but anticipate similar effects - I'll know tomorrow as we're out in it all day.
The rubber difference is more (and speedo virtually identical) though as I also reduced the rim size: 225/55/17 from 245/45/18

[HPsauce]

I haven't done much driving in the S8 with the winter setup yet, but anticipate similar effects - I'll know tomorrow as we're out in it all day.
Indeed, a smoother ride, but still good handling. Not that I was pushing it much. :tuttut:

[Dezzy]

Guy didn't you poly bush all your suspension? That will have made a big difference to the way the car handles, everything will be tighter than standard so tramlining on the road might be a trade off for handling on the track.

If you want it all soft and comfotable you'd be best off with with the stock 17" and standard suspension arms


(When I bought mine it was shod with 225x40x18 and the ride was hard and it tramlined. I changed to 225x45x18 which was an improvement but I suffered a lot of sidewall damage [here in rural France if you have to share the road you often have to run onto the grass verge and if the tarmac surface is damaged at all when you rejoin the damage rips out the inner tyre wall!].)
Chris, the profile is a persentage of the width of the tyre, so 40 or 45 of 225 isn't much different but 45 of 245 over 45 of 225 would be. If that makes any sence.

[daviesbike]

yes your right there Dezzy im still tinkering to find a happy medium strange that i drove another members s8 at one of the meets and im sure he had 19 or maybe 20 and that seemed slightly smoother than mine, i will try the 245 50 18 set up and see whats its like, think i will get part worns though, not spending on brand new tyres until i find the right choice +++

[Dezzy]

Yeah good call Guy. I have run Ovation tyres for just over a year, they have had some really bad press about stopping in the wet.
I personally have had no issues with them at all, the ABS dosen't kick in when breaking hard. They were even ok in the snow, that said they are a M + S tyre. They even did a few tame laps at Castle Combe.

I didn't take them off for the summer and i need to replace the fronts soon hence why i bought another 2, the rears still have about half left.

I wouldn't recomend them to anyone incase they had trouble but personally i found them to be fine.

They meet all EU regs and have too to be sold here. They were tested against premium brand tyres one being Michelin, now there are two ways to look at this one being the Michelins out performed the buget in this case Ovation in wet braking, dry braking and noise levels (only by 1db) and therefore the Ovations are dangerous. The other way is well they are bound to outperform the bugets and so they should @ £225 each with the Ovation being £65 each. I can almost do all 4 corners for the price of one.

I worked in the tyre trade for a while and i've seen how you sell a really expencive tyre over one that costs half or less. And i know there will be the old "well it's the only thing that connects the car to the road" and you're right it is, but heres the clanger. The tests done use probably the best all round primium tyre on the market against one of the cheapest bugets fitted to the same car in the same conditions and give the results. Is that a fair test? I could say to you my Ferrari will outstop a Vectra does that mean the Vectra is a danerous car?

[daviesbike]

very true indeed, the same as when an officer of the law pulled me over one day because he sed that i had been to heavy footed when i came to the national speed section, my reply...

why buy a ferrari if you can not go from 0-60 in 4 odd seconds as long as you do not exeed the stated speed limit there is no law to dictate just how fast you can get there,

his reply .

tooshay sir and along my merry way i went,

[Architex_mA8tey]

lol love it haha +++

[sarg]

Guy didn't you poly bush all your suspension? That will have made a big difference to the way the car handles, everything will be tighter than standard so tramlining on the road might be a trade off for handling on the track.

If you want it all soft and comfotable you'd be best off with with the stock 17" and standard suspension arms


Poly bushes will definitely make tramlining worse

[Nollywood]

I had poly bushes on my old S2 Avant, Ur quattro 20V and A4 3,0 Avant quattro. Of all the cars, the Ur quattro 20V was the most forgiving. Both the S2 Avant and A4 3,0 Avant quattro tramlined like hell, I reverted back to stock arms and bushes, and all was well.

Tramlining I can't deal with. Very dangerous, especially when overtaking a big rig, and you're not sure where your car's gonna go. Too unpredictable to be considered safe.

[daviesbike]

i agree totally, when im on a long run and i start to get tired i tend to jump and panic at the tramlining as it can be so abrupt, im using the ramp tomorrow so i think i will take most of them off maybe leave the Anti roll bar links on ect but the main things i will revert back to,