new shoes for 1991 535i e34 (rim/tire help please)

I just bought a 535i and the tires are completely bald. I want to replace them (and the rims while im at it) but i have a few questions before i do.

First off excuse me if these questions sound basic. This is my first BMW and my knowledge of cars is relatively limited to begin with.


What is the largest rim size that can fit on this vehicle without any major modifications? I've been trying to do research as best I can but different websites give me different specifications for the same vehicle. Some websites say up to 20X8.5 rims will fit but I hear tirerack.com is one of the more reliable sites as far as measurement issues and their website tells me 18X8.

In addition to rim size, If anyone has any tire size recommendations please chime in....

Im having a problem with vehicle clearance. I live in south america and a lot of the roads have poorly designed speed bumps that cause my car to bottom out quite frequently. Even when coming to a complete stop before rolling over them I still scrape the crap out of the bottom of my car so I dont believe its a matter of weak suspension either.

In theory a larger diameter tire will allow for greater vehicle clearance (though very minimal). Is this a viable option in order to get another inch or so of ground clearance?

If so, I'd like to know the largest size tire that will fit this model. If not, what else can i do to gain clearance? Is getting adjustable coil overs my only option?

Sorry for the long post, I just wanted to check with you experts since my research wasn't yielding the information I was hoping for.

Please feel free to drop any and all knowledge/suggestions my way. Much thanks to you all.

Im thinking of going 18x8 with 235/50/18 can anyone confirm this will fit without compromising the integrity of the car or posing and risks?

Any thoughts on the clearance issue?

Sorry to seem so ancy but im in a rush as these tires needed to be changed yesterday..

Thanks.

Here is a site where you can plug in differing sizes of tires and see all of the dimensions as well as compare it to other sizes visually.

http://www.miata.net/garage/tirecalc.html

Hope this helps.

Fitting 18-20 inch rims will make the ride substantially worse. When you fit a larger diameter wheel, you match it with a lower profile tire to keep the overall hieght of the wheel/tire combo near stock.

You would be much better off on the stock 15's for rough roads. Making the combo taller starts to mess with the speedo accuracy and probably starts interfering with suspension parts.

Rough roads... two words, Toyota Hilux

Yeah I'm running 18's and you're ride won't improve as there is hardly any rubber to absorb any of the bumps, my advice is to slow down man.You need to go in to the speed bump at an angle letting one wheel go over at a time. Speed bumps are made for a reason, although I'd like to shoot the guy who invented them in the face. There are some around here that are more like speed "mini hills", @Snowsled have you seen the episode of top gear where they tried to destroy that Toyota Hilux?

^^One of the greatest episodes!

18s are generally too big to feel any comfort while driving. 17s look great, but even some 16" basketweaves off an e32 (7 series) look great too, IMHO.
Also, the larger wheel you have, the more expensive the tires are, and the more likely you are to dent/deform them due to potholes. The roads are so bad where I am, the PO of my car managed to dent one of the stock 15" wheels!

Sent from my ADR6300 using Bimmer App

Thanks for the quick replies

Im not too concerned about denting the rims, I drive very carefully so thats not an issue. Also, I am not looking to make the tire too low-pro because I know will worsten the ride comfort as well. I want to maintain the handling of the vehicle but I am willing to trade a slightly higher center of gravity for more clearance.

Ive decided im definitely not going bigger than 18X8 for numerous reasons but im still interested in the setup I mentioned before...

What does everyone think of running 235/50/18 tires?

I know its not a super beefy tire but its hardly low profile either. I just looked on the site from BMW LVR (thanks! very helpful) and it is 4.6 inches of sidewall which is only .7" less than the stock setup. Seems like sufficient protection for the rim (unless ur driving on goosefoot33s road, yikes!) but if anyones differs please let me know.

snowsled7 - haha I see tonnnns of hiluxs here... they seem perfect for this terrain. those videos are nuts, toyota makes great vehicles! I actually have a lifted 5.6 pathfinder sitting on 33's for the really rough roads but its just way too expensive to drive when premium gas is upwards towards $6-7 bucks a gallon (95/98 octane, no 93 here) Id like to have the beamer as a town cruiser since its already set up to run on natural gas (lower emissions and much more economical).

m54fella - I totally know what ur saying with taking the bump at an angle, but the problem is the speed bumps in some parts are about 6-8 inches high but only about 1-1.5 feet long (from front to back as your driving over it) so there isn't really any getting around it. The mini hill ones you described are no problem. But the other more aggressive ones are a different story. No matter what angle I take or how slow I go, (believe me i take sharp angles at <1mph) the fact is my car simply doesn't have the clearance to make it over without scraping. The speed bumps are too high off the ground and too shallow in length for any type of maneuvering to compensate - your car has to have the proper clearance or it WILL scrape.

Again sorry for the long post guys just trying to cover all my bases here.

So i guess now my next question goes back to whether or not 235/50-18's are a viable option.

First of all, can this car be fitted with a tire that is 27" in diameter? Secondly, Is 4.6" of sidewall enough protection for a rim, assuming im not driving like an asshole over bumps and potholes? If not, what is the recommended minimum sidewall height when driving on less than ideal roads?

I know some of you have recommended going smaller for handling and comfort reasons but I have to admit I like the aesthetics of the 18's. 19s are too big but i feel 18's look super sharp with this body style. I suppose i could rock some 17's but is it really that much of a difference in ride comfort? going from a 235/50-18 to a 235/55-17 only increases the sidewall length 0.5" up to 5.1"

I dont drive this car very aggressively, I just like having it to cruise around town with. I need to have a safe and reliable car but if I lose a little bit of handling or ride softness at the gain of clearance and aesthetics im fine with that.


Thanks again for your time and wisdom everyone. Cheers!

IMO, I wouldn't go bigger than 18's. Normally I would only go for 17's, but since M-Pars are 18", those make an exception.

Tires for 17" wheels are also cheaper.

My car has 18's, and is also lowered, so it isn't near as smooth as my touring was. But it still isn't an absurdly rough ride either.

Gravik, you have a beautiful car, i cant believe not a single person has even posted in ur thread! if i was still in chicago id come get her off of you today.

what size tires are you runnin?

Actually what size rims also? you say 18 but what is the width? all the models i checked out from beyern were at least 8.5 inches. I really like them but i wasnt sure if they would fit on the e34 (thought 8 was the max?) so i was afraid to order...

Thanks

18x8.5 front with 235/40RZ/18 tires, 18x9.5 with 265/34ZR/18 tires in the rear.

So I think I got lost on the part where larger wheels gives greater clearance over bumps. And the reason for that is because it's completely wrong. There is only one size diameter that fits under your fender. The larger the wheel, the less the tire to fit into that diameter.

You need OE or equivalent springs. You need the smallest size wheel at or below 17 inches. Bilstein HD shocks if you want to get more serious.

Monster trucks and tractors go over holes and bumps the size of your house. And it has jack crap to do with 18 inch spinner rims. It's all springs and all rubber and the smaller the wheel the better.

Your wheel can change diameter. Your tire can't. It's simple geometry. The radius between your axle and top fender is not altered by a wheel. It's altered by increasing the radius between the fender and axle.

ThoreauHD, thanks for the reply.


technically speaking, if the fender wasn't in the way (i could get them rolled if need be and ive also been contemplating getting adjustable coilovers and raising the car 1") then say upgrading from a tire thats ~25" in diameter to a tire thats ~27" in diameter would cause the radius of the wheel to increase from ~12.5" to ~13.5. correct? (radius = diameter/2)

And while the radius of a wheel isn't always exactly congruent to the ground clearance on the vehicle, the two measurements certainly have a positive correlation (meaning if you increase/decrease one, the other will follow that direction)

This principle can be seen on many off-roading vehicles that are fitted for larger tires and gain ground clearance as a result (this additional clearance gained is a result of the wheel now holding a larger radius and thus increasing the length of matter from the axle to the ground. This is completely separate from any other modifications the vehicle might be equipped with, coilovers, body kit, lift kit etc...)

The same principle applies to my vehicle (or any vehicle for that matter) the only difference is in my case I have to overcome the problem with fender clearance.

Please correct me if im missing something. but like you said, its simple geometry - and generally speaking, a larger wheel will indeed increase the ground clearance on a vehicle.

All I have are 225/60/15 stock size tires on my 535i. All I can say is "Smooth, Fast and Quite.....................

Thanks for the response japbike.

I would definitely agree with your statement in regards to stock tires being smooth fast and quite, but recommending I stay with my current setup doesn't exactly help me with my clearance issue, which was my incentive for posting. There are specific reasons why I'm inquiring about larger wheels, feel free to read the first post of the thread for more information on my specific situation. Cheers.

No worries mate, I like them stock. I don't think the factory had vanity in mind when they built it......Cheers

Use the Tire size calculator provided BMR_LVR or this one.

http://www.1010tires.com/tiresizecalculator.asp

You need to stay within 3% of OEM OD. Within 1 % is best if you can get in that range but when changing rims that is sometimes hard to do. It may look great but try not to exceed a 17 inch rim. You sacrifice allot with an 18 or over... And driving carefully has little to do with dents when dealing with low profile tires. You drive with an 18" or 19" on an e34, they will get dents, They may be minute' and you may not even notice till you go to get new tires mounted one day :o)))

The ones in my sig pic were 17 x 8.5 front and 17x10 rear. And she was lowered. In the winter months when I would put the OEM size BBS rims on her, the ride was twice as nice :o)))

On a side note, I recently rented a 2013 Ford TORUS. It cams from the factory with 19 inch rims. Sweet... But it still had about 5 inches of tire between the road and rim. If the car is made for that, no problem :0