superstring

Hi All

I'm thinking about "upgrading" my rims and tyres from 16” to 17” on my “Classic” 98 Impreza and I’m looking for some help and advice!

I certainly like the look of 17" rims, but, from a performance standpoint, I'm concerned about a couple of things.

I'm aware (from searching on ScoobyNet) that the most common tyre sizes fitted on 17's are 205-45/17 and 215-40/17, and that, apart from the Pirelli P-Zero and the Dunlop SP 9000, there is practically nothing available in 205-45/17, while there are many more choices in 215/40-17.

However.....

1. The load capacity (load index) of most high performance 215-40/17's that I've looked at (with the notable exception of Toyo's T1s) is some 125 lbs. LESS per tyre than Subaru recommends. This of course adds up to a car that is about 500 lbs. “under-tyred” in this respect. Does anyone have any thoughts and/or experience with problems arising from this "issue"?

2. And again, from a pure performance standpoint, for those who have gone from 16" rims to 17's, has it been worth it? Prodrive's Mike Wood is on record as saying that moving from 16" to 17" rims (on a Classic) is a more important performance upgrade than changing suspension. But Prodrive recommends a 205-45/17 (preferred) or a 215-45/17 P-Zero. I presume that the 215-45/17 tyre is recommended because of its' higher load rating.

I’m also thinking that, in order to maximize the contact patch of a 215 tyre on a 17 by 7 rim, a little under-inflation is in order to flatten it out, and this may negate some advantages of the lower sidewall.... maybe I'm better off staying with my 16 inchers!?

Ideas, opinions, and educated guesses are all very welcome!!

Thanks.

John


[Edited by superstring - 10/23/2003 6:35:13 PM]

[Edited by superstring - 10/24/2003 6:51:34 PM]

superstring

Anyone??

wrxsmo

If your taking it completely from a technical point of view then stick with the 16's, thats how the car was designed. However 17's give a sharper feel & look sooo much better (but not quite as good as 18's !)

Initial D

Hi

I have a 97 Turbo five door - which was great when I drove it on the standard rims. When I got the car - Subaru put some 17in Oz rims on with Bridgestone Potenza 205/45R 17 shodded to them. I was shocked with the change. The body roll was gone - turn in feels more natural and progressive (safer!) - and the car feels so much closer to the road. Yes the looks are better - but I think that driving is more important and the larger wheels have improved that aspect in my car certainly - so the positives are very tempting.

Negatives? tire price - Both Bridgestone and P-Zero Neros are expensive to replace - curbing the wheels makes you want to cry and some over sensitive people would say that the ride is harsh (rubbish!). As for the load carrying aspect - Subaru put Bridgestone on as that was recommended by Subaru Japan as been fine to use - they have/had a lot more five doors in Japan and what are they for? Carrying heavy stuff over long distances - so they must have some idea - I have had no problems at all as yet - with dogs - shopping - big tvs etc in the back. (Just make sure you get a decent cargo net for the bendy bits!)

Good luck and let me know what you go for!

ID

superstring

Thanks for the replies!

Initial D: Are you sure the Bridgstones are/were 205/45"s and not 215/45's? It's just that I'm not aware of any Bridgstone tyre in 205/45-17.

John

Jerry B

On my '98 5dr I went from 205/50/16 Bridgestone s02's, which were pretty good, to 215/40/17 Goodyear F1 GSD3's which were absolutely awesome. Personally it took my understanding of the car's capabilities to a new level. Superb grip especially in the wet, predictable, progressive, and surprisingly not noticably harsher. My confidence increased enormously.
Recently went back to the 16's with the old S02's (4mm tread left but well worn) and felt the difference immediately.
Just put more F1's on the 16" rims again last week to sell it and they felt surprisingly good straight away, so maybe it wasn't all down to the tyre size as I had thought, but either way I didn't see any real downsides to 17's except a little harsher ride when the tread was just about illegal.

This morning I put some 17" F1's on the new car. I only got it last night and I just wouldn't be happy with those OEM RE050's on there.

I found the best pressures for me were around 33F/30R.

superstring

Jerry B

Did it cause you any concern that the 215/40-17 Eagle F1 GSD3 is rated for a maximum load of only 1074 lbs., whereas the original 205/50-16 tyres are rated around 1200 lbs.?

Cheers!

John

[Edited by superstring - 10/30/2003 8:51:10 PM]

JamesS

Have a read.....

http://bbs.22b.com/ubb/Forum1/HTML/001405.html

superstring

Thanks, James!

It would seem that the use of most 215/40-17 tyres is marginal at best (and downright dangerous at worst) on a classic scoob, from a load rating point of view. I'm surprized so many people use them. The only high performance 215/40-17 tyre that I've come across with the proper load rating (1200 lbs.) is the Toyo T1-S.

John

JamesS

I`m going for a set of 215/45R17 GSD3`s, load rating of 91.....

superstring

Seems like a prudent choice, James!

What I'm wondering now is whether there is any PERFORMANCE advantage(generally speaking)in running 215/45-17's over 205/50-16's? The sidewalls of the 17's are very slightly lower, but the overall diameter is slightly more, raising the CG up a bit!

Initial D

Have had another look and they are certainly 205/45 17 on my wheels. I will ask at the local Subaru dealer (who fitted them) what and where to get them - it could be that they came over from Japan...?

krazy

bridgestone potenza re-050 are available in 205/45/17..

Anyone tried any of the 215/40/17 tyres that are available in reinforced versions?
yokohama a539
Dunlop 8000?
etc,,

Jerry B

Is that each tyre??

I've just put some on the '03 and that's heavier still....

superstring

This is how I figure it: Classic Impreza weighs ~2900 lbs. 60% of that is on the front tyres, ie 1740 lbs. Divided by 2 = 870 lbs. on each tyre. Now, "worst case scenario" (well, maybe not quite ), driver and passenger each weighing 200 lbs. Let's say 2/3 of that extra weight is on the front, ie 133 lbs. extra on each tyre = 1003 lbs.

You can see this is getting very close to the load index rating of most 215/40-17 tyres (including the Eagle F1 GSD3) of 1074 lbs. Now, it's my understanding that the load index is calculated for a tyre inflated to its' maximum pressure (not absolutely sure about this). Obviously this maximum inflation would not be "normal" road pressure, so the load capacity may actually be less using "normal" pressures of ~33 psi. Not much of a "comfort zone"!

[Edited by superstring - 10/31/2003 5:25:02 PM]

[Edited by superstring - 10/31/2003 5:25:39 PM]

krazy

superstring I read something similar to that....
Was a rough calculation as a starting point for setting tyre pressures........ max load is at max pressure, cant remember the acutal calc. but is was along the lines of if actual load is 50% of max load then pressure is 50% of max pressure + something (~20% i think)...