Tow vehicle rims---anything I need to know?

Hello all,

I have always gotten great advice here and I'd love some input regarding something a friend recently told me.

What would you suppose the limit is on how big rims should be on a tow vehicle? I suppose I agree with him that 26"'s on low profile tires are probably not practical for a tow vehicle, but he says that even 22"'s are too much on a full size Yukon/Tahoe/Escalade.

Anyone have any specifics on this issue? I have a fiver riding on it.

I had 26's on my navigator and there was no way it could pull the boat, tires were way to thin. You might get away with it on 24's and if you had 22's there would be no problem at all. I tow with a range rover supercharged on 22's and i have no problems.

I have 22's on a full size Yukon. The tire size and rating is really the more important piece of the puzzle. I use 305/45 tires because it's the biggest tire I could fit on the stock height of the Yukon without modifications and offers sufficient sidewall to tow my Supra.

You can get away with 24's if you have room to put a big tire on it. But, even at 24" rims and towing, you may want to look into some aftermarket brake rotor and pads.

26" and up forget about it.

22's are a factory option on the 2007 Escalade. Make sure you buy quality brand name wheels, and not the $999 per set ebay specials. Find the wheels you want and call the manufacture for a load rating.

The bigger the rim, the more exponential loss of braking capacity. You will also loose acceleration. Going wider will of course give you better traction, but will also affect milage. The centrifigul forces at work play a huge part in how a tire/rim combo affect everything.

"The bigger the rim, the more exponential loss of braking capacity."

I'm trying to wrap my feeble mind around that one. Can you explain, please?

"You will also loose acceleration." I think I get this one.

As an aside - bicycles have rims; cars have wheels.


(Message edited by swass on November 22, 2006)

I put 20's on my Tahoe and it tows the boat good but the truck drives like crap. It grabs every rut in the road and rides alot rougher but it looks good. You allso have to watch when you have a beer or two at dinner when you drive home if you are on a road that has ruts you will looked liked you had more to drink then you really did.

Other than looks are there any advantages to running 20"+ wheels.

My Yukon handles alot better with the 22 x 9.5's over the stockers. Rides great too. I think it's all about the tire though.

Primarily for looks however.

Swass, I think what he means is the larger the wheel/tire, the more rotating mass (weight) the brake system has to slow (unless you spend the $$ for forged wheels, and even then the tires weight a ton). SUVs/trucks already have notoriously small brake systems and adding 20-50 lbs of wheel/tire rotating mass per corner will have a negative affect on braking performance by a large amount. It kills me to see someone with 26" chrome wheels and stock brakes.....they probably have no clue they just increased their stopping distance by like 30' or more.

NAW I had larger wheels and z rated tires on a car that I had. They looked nice but I did not like how they followed ruts, wore out super fast, were expensive to replace, rode worse than normal tires. They did make the car handle differently. I would say better for racing but for street driving they were no better than the normal tires.

I went thrue 3 sets of tires in different sizes and finally just took the wheels off and put stock tires back on because they were too expensive to replace and SUCKED in the snow.

I understand how a larger tire, has more rotating mass. ... 1st Semester Physics.

My question is: How does this overwhelm the weight of the vehicle. Isn't stopping the vehicle (almost 2 tons) more of the equation, than the tire/ wheel mass?

I don't know the first thing about physics, but I've bolted on lots of oversized wheel & tires, and they will dramatically increase the stopping distance. My buddy Richard put 20" rims with 36" swampers on his suburban, and I had the same setup on my tahoe. They both scared me a couple of times. That is why I spent about twice as much money on forged billet wheels for my new truck. They weigh quite a bit less than standard cast wheels, so the braking effects are not as bad.



(Message edited by humboldtboarder on November 22, 2006)

Its a flywheel effect, so-to-speak. Now the wheels/tires have much greater leverage on the brake disc and axle b/c of the increased rotating mass and the distance of that mass from the axle centerline.

Unsprung and rotating mass has a very large impact on vehicles performance, even more so than its gross weight. What I mean is adding/losing 400lbs to the overall weight will effect its performance, but adding/losing 100lbs of rotating, unsprung mass will have a far greater effect.

Thats another ballgame Nick J, changing the overall circumfrance of the tire does change braking. Going with a larger wheel does not change the braking that much, as long as you are getting the proper size tire that keeps the OEM circumfrence similar. However, I do agree with Ryan...SUV/Truck brakes are a joke...people spend crazy amounts of money on tires, wheels, engines, suspension, and then leave the brakes stock. Meanwhile, those of us in the performance car arena spend 1/3-1/2 of our upgrade money on upgrading braking systems. I have almost 3x more rotor surface on my S4 than my Tahoe. Another partial truth/myth is that bigger brakes alow you to stop faster...kinda sorta....they do allow you to stop faster the 3rd,4th,5th,etc consecutive time you hit the brakes. Try doing 3-4 consecutive 60-0 stops in your SUV and see how much brake fade you get.

Increasing the weight(bigger wheels) would have the same effect as increasing the circumference. Centerline wheels says that adding 1 pound of rotating mass is the same as adding 8 pounds of static weight.

Ihave 24's on my Infinity QX56...No problem

Its a calculation of the total diameter of the wheel + tire sidewall height that is used to calculate circumfrance. Unfortunately they use inches for wheel diameter, and millimeters for tire crosswidth and sidewall height, which makes the calculations confusing. When you increase the wheel diameter by 1", you will usually decrease your aspect ratio by 5-10%. The sidewall height is calculated like this for a 275 70R17 tire:

275mm * 0.70 = 192.5mm.

For a 305 45R22:

305mm * 0.45 = 137.25mm

192.5mm - 137.25mm = 55.25mm. With 25.4mm per inch, that equals 2.17 inches less sidewall height. Multiply this by 2 for each sidewall and you have a decrease of 4.4 inches in sidewall for the 305 45R22. Since there is an additional 5 inches of wheel over the 275 70R17 you have an overall increase in diameter of about 1 inch. Divide this by 2 for the radius and you can figure the vehicle will sit 0.5 inches higher.

So as the wheel size increases the tire sidewall height decreases, keeping the diameter of the 275 70R17 within an inch of the 305 45R22. However, this 1" in diameter increase will reduce the number of rotations per distance traveled. This means your speedometer will read lower than actual, and it will increase the resistance needed by the brakes to stop the vehicle since the radius from the center of the hub to the road has changed.

The stock setup with the additional sidewall height will absorb road bumps better, and the manufacturer of the vehicle likely calibrated the suspension and steering for the 275 70R17 wheel/tire combo, so the ride and handling will change. You may also get some tire rub on the vehicle frame when you turn steering to full lock when manuvering in a parking lot with your trailer.

I have 22's on my 07 Denali. You do substitute a little bit of ride for the look, but worth it if you set it up right. I think my tires are 285/45/R22. This is the closest size to the factory tires as far as overall height. It only affects your mileage slightly. 1 mile = .999 after the switch. If you have the tire sensors that track air pressure get them put in the new set-up as well because they actually will automaticall update the transmission shift points. True at least on the GM vehicles. Think