Lower profile tires -- how careful do I need to be

[rationull]

My new car has wheels/tires that are set up more for high performance than my last car. As is the trend these days that means lower profile tires. Nothing too extreme, though: these tires are 235/45R17 where my last ones were 205/55R16. If my calculations are correct, that's a sidewall height of 4.16 inches vs 4.44 inches with the old ones. That number sounds a little high to me just based on eyeballing the tires, but in any case it's not that big a difference, so I suppose I shouldn't worry about it.

But just a reality check: How much does the risk of wheel damage on rough roads increase with shorter sidewalls? Not necessarily talking about hitting a killer pothole at 90 mph, but I occasionally have to do some low speed driving on dirt roads that are, shall we say, less than perfectly maintained. I'm talking eroded rural driveway kind of stuff, not "real" offroading.

How careful does one need to be? How much of a buffer do the OEMs include when they spec wheel construction and tire sizes?

 

[bepperb]

A lot of the sidewall is hidden behind the wheel. I doubt there will be much difference. The main concern I'd have either way would be bottoming out the car, not damaging the wheels.

 

[CapriRacer]

Personally, I think the OEM's have moved to lower profile tires faster than they should have. By that I mean the suspensions haven't quite kept pace developmentally and the lower profile tires are being forced to absorb more of the impact energy - and that results in failures.

If I were you, I'd add 3 to 5 psi over what the vehicle tire placard says.

 

[Quattro Pete]

I have the same size tires on my 530i. In my experience, you need to be somewhat careful, but not overly so. As long as you keep the speeds low, there shouldn't be a problem. My OEM wheels are still OK.

 

[HTSS_TR]

I agree with CapriRacer. My E430 OEM tire is 235/45-17, I always inflate the tire to 4-6 PSI above placard for local driving and 8-10 PSI for long distance and high speed(above 90-100 MPH) driving. No wheel damage after 12 years 130+k miles.

 

[SteveSRT8]

ran 275/40/20 on my factory wheels for years, just switched to 275/35/20.

Factory recommended is 32 psi, but I prefer 34 (cold)

I have hit huge potholes at 55 mph with a full compliment of passengers (5) and all their luggage. never a peep. almost 6 years now.

 

[rationull]

Not too concerned about bottoming out. The car's got enough clearance and I'm talking low speeds here (less than 10 mph -- although steep uphill grades make it problematic to go much slower).

Upping the pressure sounds good to me. I'm used to running 4-5 PSI higher than recommended in my other vehicles. The new one is an AWD though and recommends 1 PSI higher in the front. I guess I should vary it by about the same amount if going higher than recommended?

The car is a Subaru, and IMO they've got their suspension tuning a little better sorted out on their performance models than some manufacturers. The seem to have enough suspension travel and bounce in general without relying on the tires or providing an overly harsh ride. IMO at least, I don't have a huge sample size!

 

[oggb]

My WRX had 17" wheels with low profile tires. I have five (5) OEM wheels for that car, four of which are bent and cause vibration that a roadforce balancer can't get rid of.

 

[rationull]

Originally Posted By: JRed
My WRX had 17" wheels with low profile tires. I have five (5) OEM wheels for that car, four of which are bent and cause vibration that a roadforce balancer can't get rid of.


Ouch. What happened to them?

 

[rjundi]

My wife hits things and the area where she works does not take of roads (MA). She has 215/45/17's on her Subaru turbo legacy wagon and we have wrecked two tires in different sets. Thankfully one was in a well worn set so replaced all four. The second one was covered by first 2/32" wear free road hazard by Conti.

Both times she hit manholes raised up, once at 80MPH another time sliced our tire in middle of busy intersection.

The rims seem to balance fine and had car up to 85 MPH (her commute speed) no vibrations.

 

[Astro14]

Originally Posted By: rationull
My new car has wheels/tires that are set up more for high performance than my last car. As is the trend these days that means lower profile tires. Nothing too extreme, though: these tires are 235/45R17 where my last ones were 205/55R16. If my calculations are correct, that's a sidewall height of 4.16 inches vs 4.44 inches with the old ones. That number sounds a little high to me just based on eyeballing the tires, but in any case it's not that big a difference, so I suppose I shouldn't worry about it.

But just a reality check: How much does the risk of wheel damage on rough roads increase with shorter sidewalls? Not necessarily talking about hitting a killer pothole at 90 mph, but I occasionally have to do some low speed driving on dirt roads that are, shall we say, less than perfectly maintained. I'm talking eroded rural driveway kind of stuff, not "real" offroading.

How careful does one need to be? How much of a buffer do the OEMs include when they spec wheel construction and tire sizes?


While they handle great, the 235/45R17s on my car have little give over sharp edges/impacts...fine where roads are smooth...and while I have yet to damage a rim...I bet they're more susceptible to the impact damage...

 

[leeharvey418]

Just to add to what Capri said earlier about OEMs not making suspensions robust enough - it's not just the impact harshness that beats up suspensions. Suspensions that are designed around the dynamic loads from a wheel and tire package that weighs, say, 45 pounds will see drastically reduced fatigue life from the loading increase associated with going to a package that weighs more. The stock package on my RAV4 weighs about 53 pounds, but I could fit a package that weighs 65+ pounds per corner without trying too hard. That increase would cut fatigue life by roughly a quarter (assuming that the wheel and tire accounts for about 60% of unsprung weight).

 

[George Bynum]

Originally Posted By: SteveSRT8
ran 275/40/20 on my factory wheels for years, just switched to 275/35/20.
You've dropped 4 (8 if OE were XL and new are standard) in load rating ... I'd verify you haven't put yourself in an overload situation ... think Ford and Firestone ...

 

[Scum_Frog]

My Jetta 2.0T hs 225/45/17's and we just drive as normal..... but I do try to keep the potholes manholes down to a minimum if possible

 

[Rand]

Originally Posted By: George Bynum
Originally Posted By: SteveSRT8
ran 275/40/20 on my factory wheels for years, just switched to 275/35/20.
You've dropped 4 (8 if OE were XL and new are standard) in load rating ... I'd verify you haven't put yourself in an overload situation ... think Ford and Firestone ...


Where did this come from? considering he didnt list the brand/model of tires

 

[SteveSRT8]

Originally Posted By: George Bynum
Originally Posted By: SteveSRT8
ran 275/40/20 on my factory wheels for years, just switched to 275/35/20.
You've dropped 4 (8 if OE were XL and new are standard) in load rating ... I'd verify you haven't put yourself in an overload situation ... think Ford and Firestone ...


Nah, it wasn't a quick decision. Factory shipped with 245/45/20 Eagle RSA's.

Hankook Ventus V12 evo's. 275/35ZR20 102Y XL.

One of the reasons they were used is they are designed for heavier vehicles. And the high speed rating is a must on this car!

 

[HTSS_TR]

275/35-20 is 3.8% smaller than 245/45-20. The better fit is 275/40-20.

 

[SteveSRT8]

I agree. Thanks for the concern.

I knew all that, it was a matter of the proper size not being available.

My aftermarket programmer allows me to plug in almost any tire size and keep all nine computers happy.

Plus, I like the gearing advantage!

 

[oilmaven]

I can't believe how large wheels have gotten...and how thin the low profile tires are. I didn't have to wince and dodge every pothole with my '82 Chevrolet Citation...if memory serves, it had 185 80 13 tires. They were like balloons...and handled like it too.