Tire Deflection, How Much Room |
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Tire Deflection, How Much Room |
NARP74 |
Aug 15 2022, 01:51 PM
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#1
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Senior Member Group: Members Posts: 1,066 Joined: 29-July 20 From: Colorado, USA, Earth Member No.: 24,549 Region Association: Rocky Mountains |
I am looking into some rear fender work for tire clearance. How much room do I need for tire clearance to be safe? Is it the same for inside v outside clearance?
Narrow body, no flares, 215-55/16 tires. |
Front yard mechanic |
Aug 15 2022, 03:07 PM
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#2
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Senior Member Group: Members Posts: 1,164 Joined: 23-July 15 From: New Mexico Member No.: 18,984 Region Association: None |
Go to Tacoma world tire calculator and punch in your tire size and the stock tire size. It will give you the actual tire dimensions and a side by side overlay. My 205/60/15 clear but just barely on full turn. (IMG:style_emoticons/default/smash.gif)
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NARP74 |
Aug 15 2022, 03:14 PM
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#3
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Senior Member Group: Members Posts: 1,066 Joined: 29-July 20 From: Colorado, USA, Earth Member No.: 24,549 Region Association: Rocky Mountains |
Not looking for size info, have done a bunch of that. Looking for how much clearance I need on the inside and outside of a particular tire so the tires don't rub anywhere in the rear of the car. How much will a tire generally move side to side while driving.
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Front yard mechanic |
Aug 15 2022, 03:31 PM
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#4
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Senior Member Group: Members Posts: 1,164 Joined: 23-July 15 From: New Mexico Member No.: 18,984 Region Association: None |
235 /35/ 20 on the gts 911 has zero deflection you could use those
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NARP74 |
Aug 15 2022, 03:34 PM
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#5
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Senior Member Group: Members Posts: 1,066 Joined: 29-July 20 From: Colorado, USA, Earth Member No.: 24,549 Region Association: Rocky Mountains |
What kind of answer is that? I can't run a 20 inch wheel on a narrow 914.
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porschetub |
Aug 15 2022, 04:28 PM
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#6
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Advanced Member Group: Members Posts: 4,699 Joined: 25-July 15 From: New Zealand Member No.: 18,995 Region Association: None |
What kind of answer is that? I can't run a 20 inch wheel on a narrow 914. (IMG:style_emoticons/default/chair.gif) my rear clearance is with 16x7'' fuches and 205 /50/16,my guards are pulled a little and I have no rear trailing arm shims,I can get the tips of 4 fingers in the gap so I would expect you will need to roll the lips or cut a half moon in them with 215 's. Good luck. |
brant |
Aug 15 2022, 04:32 PM
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#7
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914 Wizard Group: Members Posts: 11,624 Joined: 30-December 02 From: Colorado Member No.: 47 Region Association: Rocky Mountains |
the amount of deflection would really depend on the tire brand and sidewall height...
a 50 series tire will deflect less than a 60 series... etc. |
NARP74 |
Aug 15 2022, 04:42 PM
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#8
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Senior Member Group: Members Posts: 1,066 Joined: 29-July 20 From: Colorado, USA, Earth Member No.: 24,549 Region Association: Rocky Mountains |
What kind of answer is that? I can't run a 20 inch wheel on a narrow 914. (IMG:style_emoticons/default/chair.gif) my rear clearance is with 16x7'' fuches and 205 /50/16,my guards are pulled a little and I have no rear trailing arm shims,I can get the tips of 4 fingers in the gap so I would expect you will need to roll the lips or cut a half moon in them with 215 's. Good luck. Not stuck on running the 215s, they came with the car. Still seeing what my options are. I don't think this was ever on the street, just a dream build for someone. Theory, not reality. |
NARP74 |
Aug 15 2022, 04:42 PM
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#9
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Senior Member Group: Members Posts: 1,066 Joined: 29-July 20 From: Colorado, USA, Earth Member No.: 24,549 Region Association: Rocky Mountains |
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Superhawk996 |
Aug 15 2022, 04:44 PM
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#10
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914 Guru Group: Members Posts: 5,827 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch |
I am looking into some rear fender work for tire clearance. How much room do I need for tire clearance to be safe? Is it the same for inside v outside clearance? Narrow body, no flares, 215-55/16 tires. 10-12 mm minimum would be a good starting point. Personally, I want more if I can get it. 12mm is less than the width of your index finger for most people - that isn't much. When OEM does a motion study to check clearances they get a tire model from the tire supplier that includes all potential variation of tire dimensions within production tolerances (OD, width, lateral load deflections, what rim width it's used with, etc.) and also accounts for dynamic growth of the tire OD at maximum vehicle speed. That tire model is then cycled through it's range of motion with some allowances for worn suspension bushings. The 10 mm is a do not violate zone on top of the tolerances noted above. It is to make sure tires never contacts sheetmetal. I've seen the 12 mm violated to a soft contact with a wheel well liner which itself was still 5-6 mm from the nearest sheetmetal. |
NARP74 |
Aug 15 2022, 04:52 PM
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#11
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Senior Member Group: Members Posts: 1,066 Joined: 29-July 20 From: Colorado, USA, Earth Member No.: 24,549 Region Association: Rocky Mountains |
I am looking into some rear fender work for tire clearance. How much room do I need for tire clearance to be safe? Is it the same for inside v outside clearance? Narrow body, no flares, 215-55/16 tires. 10-12 mm minimum would be a good starting point. Personally, I want more if I can get it. 12mm is less than the width of your index finger for most people - that isn't much. When OEM does a motion study to check clearances they get a tire model from the tire supplier that includes all potential variation of tire dimensions within production tolerances (OD, width, lateral load deflections, etc.) and also accounts for dynamic growth of the tire OD at maximum vehicle speed. That tire model is then cycled through it's range of motion with some allowances for worn suspension bushings. The 10 mm is a do not violate zone on top of the above. It is to make sure tires never contacts sheetmetal. I've seen the 12 mm violated to a soft contact with a wheel well liner which itself was still 5-6 mm from the nearest sheetmetal. Now we are getting somewhere. So that on both sides? Gives me something to measure to. Thank you |
Superhawk996 |
Aug 15 2022, 05:00 PM
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#12
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914 Guru Group: Members Posts: 5,827 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch |
So that on both sides? Gives me something to measure to. Thank you All the way around in 3 dimensions. The problem with what we do with hobby cars are there are so many unknowns. The main thing you want to be concerned about is whether it clears at all ranges of suspension motion. If it were me, I'd want to check by pulling the shock and spring and then cycling the wheel and tire though a full range of motion. That is a bit hard to do without also loosening the rear trailing arm pivots due to bushing wind up. You can probably get to full jounce using a floor jack. Full rebound won't be achievable without some method of pulling down on the trailing arm or loosening the pivot shaft. Jounce travel is more important that rebound since the wheel / tire is going to be moving up into the wheel house where things get tighter to the sheet metal and fender lip. To a degree you're going to have to just make sure you have room for deflections. Rims/hubs/bearings/trailing arms flex under max lateral load more than you would think. |
NARP74 |
Aug 15 2022, 05:10 PM
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#13
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Senior Member Group: Members Posts: 1,066 Joined: 29-July 20 From: Colorado, USA, Earth Member No.: 24,549 Region Association: Rocky Mountains |
I worry more about travel on my off road vehicle than I will on this, but I will check it. don't want surprises.
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Superhawk996 |
Aug 15 2022, 05:18 PM
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#14
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914 Guru Group: Members Posts: 5,827 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch |
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