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**nando** · 10-02-2005, 04:49 PM

your fuel economy will go down slightly (since you will have to turn more RPMS to go the same speed) and your speedometer will be off, but otherwise there aren't any large drawbacks to running slightly undersized.

**EtaSport** · 10-02-2005, 05:17 PM

I may consider it if I decide to run the 15s in the spring time next year. That is unless I just dont care about money by that time. I may just run the 14s for awhile and get a set of TAs with a 500 treadwear rating. There isnt a need for decent tires over here.

**Brew** · 10-02-2005, 06:49 PM

Originally posted by nando

your fuel economy will go down slightly (since you will have to turn more RPMS to go the same speed) and your speedometer will be off, but otherwise there aren't any large drawbacks to running slightly undersized.

You forget to mention that it looks retarded.

**arsevader** · 10-02-2005, 07:09 PM

Originally posted by EtaSport

I want to stick with falkens cause they are cheap perform well and have 360 treadwear.

The treadwear rating of tires can only be compared to tires from the same manufacturer.

Originally posted by EtaSport

205 55 15s are way overpriced since I can get 225 50s for cheaper. I may get this size if money allows but what about 205 50s? I know they are undersized but how unpractical is it?

Not unpractical, you'll just have a shorter sidewall. Not sure if the price differnece is really worth it though.

Originally posted by EtaSport

Wider tires wear faster from what I read. I've had 2 years on my current falkens and they have plenty of life left minus the camber wear.

Can't really see this being true. Wider tires are usually softer compounds but the width shouldn't affect treadwear. Plus your contact patch does not increase as you go with a wider tire, it just gets wider.

James

**royalflush313** · 10-02-2005, 07:45 PM

With 205/50's the speedo will be off by 3.8% (too fast). If anything, it will save you from speeding tickets!

205/50's are so readily available and a lot cheaper (at least where I live). There are lots of VWs, Honda guys etc selling used tires for next to nothing too.

As for gas economy difference, it is probably as insignificant as the quicker 0-X acceleration that you might gain from an undersized tire...

**Mystikal** · 10-03-2005, 10:03 AM

Wider tires have better wear. The weight is spread across more tread.

In my experience, the 512's really don't offer the kind of treadwear you'd expect from a 360 rated tire. They were wearing at the exact same rate as my old 200 rated RT-215's, and the RT's were driven MUCH harder.

Not sure, but to me undersized tires would lead to an even more exaggerated camber geometry, and worse wear. I haven't put much thought into it before this post, but think about it.

A larger tire (225/50 instead of 205/50) also has a longer contact patch. So, it's wider and longer. Guess which one has better traction?

**arsevader** · 10-03-2005, 10:16 AM

Originally posted by Mystikal

A larger tire (225/50 instead of 205/50) also has a longer contact patch. So, it's wider and longer. Guess which one has better traction?

This isn't true unless you change the weight of the car or tire pressure.

A wider tire has a wider and shorter contact patch but offers the same actual contact area as a narrower tire on the same vehical. The contact area is detirmined by the tire pressure and weight of the car not the width of the tire.

James

**e30evolution** · 10-03-2005, 10:37 AM

it has a larger rolling diameter (circumferance).....~the same percentage of the rollingdiameter will be contacting the ground when size is changed... larger size=larger contact patch

**arsevader** · 10-03-2005, 10:42 AM

Originally posted by e30evolution

it has a larger rolling diameter (circumferance).....~the same percentage of the rollingdiameter will be contacting the ground when size is changed... larger size=larger contact patch

You are right there, didn't see the sidewall ratio was the same, so a larger tire overall.

James

**Mystikal** · 10-03-2005, 10:45 AM

Originally posted by arsevader

This isn't true unless you change the weight of the car or tire pressure.

A wider tire has a wider and shorter contact patch but offers the same actual contact area as a narrower tire on the same vehical. The contact area is detirmined by the tire pressure and weight of the car not the width of the tire.

James

James, your theory applies only to tires of the same diameter (which I didn't compare), and only when the car is at rest. When there are lateral loads on a tire, more of the available contact patch will be touching the pavement, and the wider section width tire will provide more traction. Hence why wider tires, all other factors being equal, are faster in timed events.

**EtaSport** · 10-03-2005, 07:51 PM

I get what most are posting up. 225/50 is still my top choice in getting new tires. I see what you mean about more possible camber with 205s. I dont drive my car that hard, and I've had my falkens on two seasons now. Probably around 20-22k miles on them, they wore fairly even with my bav-auto springs.

I think I'll wait until I am either ready, or able to buy the 225s. I can run the bcaps on the 60 profiles down here in the city. Thanks

**arsevader** · 10-03-2005, 09:12 PM

Originally posted by Mystikal

James, your theory applies only to tires of the same diameter (which I didn't compare), and only when the car is at rest. When there are lateral loads on a tire, more of the available contact patch will be touching the pavement, and the wider section width tire will provide more traction. Hence why wider tires, all other factors being equal, are faster in timed events.

Yeah I wasn't paying attention, I didn't see that both tires were a 50 series sidewall.

Though lateral loads change the position of the patch, I still don't think that the patch would be larger, as the load shifts from one side of the tire to the other, the opposite side will lift.

You are right though that wider tires provide bettter traction, but not because of the size of the contact, but the width.

James

**nando** · 10-04-2005, 08:44 AM

Originally posted by Brew

You forget to mention that it looks retarded.

205/50 would look fine, it's barely undersized. it's not like he's stretching these onto a set of 16x10 borbets or something. I had 195/60 on my ix and it actually looked pretty damn good..

**arsevader** · 10-04-2005, 09:05 AM

Originally posted by nando

205/50 would look fine, it's barely undersized. it's not like he's stretching these onto a set of 16x10 borbets or something. I had 195/60 on my ix and it actually looked pretty damn good..

I also had 195 /60 14 on my 85 325e which was the stock size untill they changed it to 195/65

James

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