11-15-2015, 02:53 AM | #1 |
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Tire wear on lowered vehicle?
I have X4 35i M (same chassis and ride height as X3) with 20" staggered wheels and adaptive shocks. Writing on this forum since there seem to be nobody on X4 forum with H&R.
I lowered the vehicle about a year ago (H&R, 35mm) and have since driven about 10000 km (6000 miles) on my summer tires - winter tires and 9000 Turbo for short runs. I work from home. I did not check alignment after lowering - nor measure depth of thread. Total mileage 14000 km, of which 2000 km on winter tires and 2000 km before lowering. I will soon put on my winterwheels and wanted to measure tire wear on summertires. I measured front tires, but it is awkward to measure rear tires - will do when removed. Tires are staggered 20" Pirelli P Zero Run Flats. Indicative results on front tires: middle 6.8 mm, outside left and right:6.5 mm. Rears seem to have somewhat less thread. I assume they were made with an even thread of 8 mm - anyone know? Front tires would then last about further 30.000 km - depending on uneven wear. That is OK - rears are worse. Since I can`t go back to normal ride height - see picture - only options are alignment and reducing tire pressure - now at 2.6 bar. I welcome any input. |
11-15-2015, 05:00 AM | #3 |
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Tyres will wear more the firmer the set up, more so on cars like BMWs that have more negative camber than other cars, same reason run flats wear so much more quickly on the inside edge too.
Seen loads of BMW with cords showing on the inside edge while still got 7mm on the outside due to run flats. I would consider getting the geo looked at, have a search for people who have lowered other BMWs and see how much they reduce the camber by when lowering? |
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11-15-2015, 07:28 AM | #4 |
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GizzE: thanks for tip - I will await final measurements after change to winter set.
Remembering pictures of low BMW:s, they go with the increased negative camber Anybody know what camber there is front/rear on X3/X4? There is a risk of increased negative camber when lowering, which would be consistent with better grip on outside wheels in a curve. After mulling it over,I am more and more in favour of increasing tire pressure. From 2.6 to 3 bar? Anybody with experience? |
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11-15-2015, 08:22 AM | #6 |
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Being Sunday, I took my "carpenter alignment tool" and made rough measurements of cambers.
Front wheels: minus 0-0.5 degrees. No sweat. Rear wheels: minus 2-3 degrees. A bit of a problem: I believe handling will benefit from negative camber in rear, but is this too much? And yes - I agree - higher ty re pressure would then lead to increased wear on rear tyres inside. |
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11-15-2015, 10:22 PM | #7 |
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these were the alignment results on my X3 after I lowered it on Eibachs... with the 20s on the same Pirelli PZero RFTs as you.
Sorry - I did not have an official print out so I was left with snapping a picture of the results off their monitor. I have not pulled off the tires yet to check the wear. but we put on about 15,000kms since last Sep 2014. Mind you, the X4 was set lower than a stock X3 to begin with so perhaps your alignment settings will be different. |
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11-16-2015, 12:55 AM | #8 |
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pokerface: Thanks! Very valuable INFO.
I believe X4 has same ride height as X3, due to US tax favoring SUV:s - which means 8" ground clearence. After your input, my only concern is rear camber - I have rouhgly - 2 to3 degrees, while spec is 1.5. I will probably reduce to 1degree. With the wide rear tires, there will obviously be more wear on the inside. As was pointed out - with negative camber - there will be more inside wear, the higher the tire pressure- I will probably reduce rear to 1.4 bar when summer tires - when light load. I will get back with better measurements end of week, when I have put on winter wheels. |
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11-16-2015, 06:26 AM | #9 | |
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I don't follow your comments on tire pressure. If you are still on your RFTs then you need to keep the pressures on the high side, or you wear off the inner edge. It is well established that low pressures contribute to the excess inner wear. Low pressure equals running on the sidewalls, the inner one at that, due to excessive camber. Raising the pressure means the crown of the tire takes more load. It is the same old issue of balancing inner wear against mid tire wear. RFTs are more sensitive to pressure settings, you must spread the load, get some of it off that inner sidewall, increasing the pressure does that, lowering the pressure loads the shoulder/sidewall even more. You don't want something like this. HighlandPete |
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11-16-2015, 07:52 AM | #10 |
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Pete. That was my first reaction,and it is valid if zero camber - riding on center of tyre if high pressure. Rear tyres are 20"- 265/35.
Situation with ultra low profile tyres with 2-3 degrees (perhaps even 1.5 degree) is somewhat unclear. My reasoning was that at high pressure, tyre would ride on shoulder, while at lower pressure, tyre will be "deformed" and more rubber in contact with road. Anyhow I will measure tyres - I get headache spelling tyres/tires -on friday, to see what damage has been made. Visually it is not too bad. I will set rear camber at 1 degree - and, probably, keep STD pressure. |
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11-16-2015, 11:22 AM | #11 | |
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RFTs are even more sensitive to pressure variation, as the sidewall's lack of deformity is less forgiving at the lower end of the pressure range. Made even worse as we add camber, as the tire is much less able to accommodate the geometric positions. Remember camber causes a tire to take a conical form/path, RFT sidewalls are not so accommodating as a conventional tire with its more flexible sidewalls. HighlandPete Last edited by HighlandPete; 11-16-2015 at 11:35 AM.. |
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11-16-2015, 03:23 PM | #13 |
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I'm surprised you didn't do a $100 alignment after installing springs. Everything I have read, including on spring manufacturer websites, indicates that you should do an alignment afterwards. Ideally I suppose after a week of driving, to let them settle, or at the very least, right after the install, if you don't feel like going back for a 2nd visit.
Here's a link to Eibach's for example: http://eibach.com/america/en/perform.../pro-alignment |
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11-17-2015, 03:06 AM | #14 |
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Lotus: BMW dealer quoted me SEK 8.000 ($1.000 US) to change springs and SEK 2.000 ($ 250) for alignment. I got springs done for SEK 3.000. Shop cold not do alignment on BMW.
I was surprised of level of handling improvement: -less wind sensitivity -improved straight ahead stability -improved steering precision -improved steer-into -a-curve -and - of course -somewhat less chassis comfort Now it is as good as MY 1997 9000 Turbo- regarding handling - better in other aspects. I decided to wait this year - measure tires and adjust whatever is needed - I have worked in the auto industry - partly for the General - and is a little sensitive of being robbed. My only concern after data from Highland Pete is rear camber. I will know more on Friday after thorough measurements. Highland Pete: how is your ride height with Eibachs, compared to mine? Consequencies of lowering? Last edited by Tjalle; 11-17-2015 at 03:24 AM.. |
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11-17-2015, 06:19 AM | #16 |
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pokerface: sorry, I got data from you - I mixed it up. Thanks.
H&R decreased ride height with 1.5". With limited lowering, I assume it would be difficult to notice any change in performance. |
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11-17-2015, 09:46 AM | #17 |
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Actually, even with very mild lowering the responses are a fair bit firmer. I'm not really aiming to slam the X3, I just wanted better handling, to which I think I have achieved it via the Eibach spring.
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11-20-2015, 02:54 AM | #18 |
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More accurate measurement of camber indicates OK values: about -1.0 front and -1.5 rear.
Depth of thread:mm LF --------------------------- RF 6.6 7.0 7.0----------- 6.7 7.2 6.4 LR--------------------------- RR 6.0 5.4 6.0------------ 6.0 5.2 5.4 Presumably ?? new tires are 8.0 mm - anybody know? All in all 1200 km on tires. Obviously vehicle drives primarily on rear wheels My concern is RR Any suggestions? BMW recommends 2.4-2.8 bars front and 2.8-3.2 bars rear depending on driving situation for 20" My first thoughts are to go to 2.8 front and 2.4 rear. I am mostly driving with light load. |
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11-20-2015, 11:25 AM | #19 |
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11-21-2015, 12:38 AM | #20 |
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Lotus: No INFO on Tire Rack - nor Pirelli - homepages.
Obviously there is no problem with camber. I.e BMW has done its homework - camber does not change with loaded vehicle - so does not track= good stability/grip even on bumpy roads. I have done further analysis: rears will last for total three years and front five. I can moderate wear with my other car - and the throttle This is better than expected for front and worse for rear- I can live with that. I will reduce pressure rear to 2.3 and increase front to 2.9. 2.3 is a bit tricky - less room for bad roads- but since I can monitor pressure with TPMS - no sweat. Add pressure in rear if heavily loaded. Wintertires will go with: 2.8 front and 2.4 rear except for when skiing (heavily loaded), when 2.8 also rear. |
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11-21-2015, 06:33 AM | #22 |
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Law of physics.
As seen by measurements, rear middle thread depths are less than outers=riding on central part= too high pressure. I often drive vehicle with light load. Front middle thread depth higher than outers= too low pressure. Have you ever had oversized superwide 20" rear tyres? |
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