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Wheels & Tyres Forum Please discuss wheels or tyres (for all vehicles) in here.

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Old 05-04-2017, 09:26 AM   #1
Type2fan
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Default Tyre pressures

Hi
I've just got some Fuchs alloys for my 78 bay. What tyre pressures are you guys using?
I've got 155 65 15s at the front and 185 65 15s at the back.
Cheers
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Old 05-04-2017, 12:15 PM   #2
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Stock tyre pressures, no matter what wheel/tyre combo as it's based on the weight of the vehicle.
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Old 05-04-2017, 04:54 PM   #3
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Thanks mate
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Old 06-06-2017, 04:10 PM   #4
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Originally Posted by Stu_b View Post
Stock tyre pressures, no matter what wheel/tyre combo as it's based on the weight of the vehicle.
Sorry to contradict, but wrong, wrong, wrong. The contact patch size changes with tyre size, therefore the pressures require changing also. You wouldn't use stock 17psi with 125s on a cal look and 285s on a Baja, would you! The narrow tyres would require a higher pressure so they don't wear the edges, and wider tyres require a lower pressure so they don't wear the centre.

My wide mountain bike tyres require 60psi, my skinny road bike tryes 130psi - same weight of vehicle...

To get even tread wear on my 215/75 x 15s on a Bay requires 27psi front and 35psi rear, giving me perfectly even tyre wear over the 130 000km I have driven it. A previous Beetle had 205s front at 15psi and 225s at 24psi the rear to avoid wearing the edges. With the sizes you quote you will need considerably higher than stock pressure up front and probably a little more than stock at the rear, and make sure they are properly load rated.

Cheers, Carl.
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Old 28-10-2018, 12:00 PM   #5
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Default tyre types & pressures

Thought I would add to this thread by saying - have you read http://www.ratwell.com/technical/Tires.html
Thus standard tyres must be commercial grade with stiffer side walls.
Note his comments about cornering loads & somehow then apply to lower profile tyres.
He then gives a lot of detail about using larger rims.
All in all following his details should end up with a safe ride.

Hope this helps every one & not too many of you find your self saying 'oh shit!'
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Old 31-10-2018, 01:45 PM   #6
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Quote:
Originally Posted by Beetlebank View Post
Sorry to contradict, but wrong, wrong, wrong. The contact patch size changes with tyre size, therefore the pressures require changing also. You wouldn't use stock 17psi with 125s on a cal look and 285s on a Baja, would you! The narrow tyres would require a higher pressure so they don't wear the edges, and wider tyres require a lower pressure so they don't wear the centre.

My wide mountain bike tyres require 60psi, my skinny road bike tryes 130psi - same weight of vehicle...

To get even tread wear on my 215/75 x 15s on a Bay requires 27psi front and 35psi rear, giving me perfectly even tyre wear over the 130 000km I have driven it. A previous Beetle had 205s front at 15psi and 225s at 24psi the rear to avoid wearing the edges. With the sizes you quote you will need considerably higher than stock pressure up front and probably a little more than stock at the rear, and make sure they are properly load rated.

Cheers, Carl.
Sorry, you are wrong. Vehicle weight is what counts, not size of tyre. Uneven wear is due to tracking/toe and camber being out, not pressure.
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Old 18-01-2019, 01:51 PM   #7
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Sorry, you are wrong. Vehicle weight is what counts, not size of tyre. Uneven wear is due to tracking/toe and camber being out, not pressure.
So you would run exactly the same tyre pressure on a 125/80 x 15 as a 345/30 x 20 tyre with the same loading? Please supply your data and reasoning.
I think you need to do a bit of reading up before your misinformation lands someone in a ditch.
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Old 18-01-2019, 01:59 PM   #8
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Yes, if the vehicle weight is the same.The reasoning is clearly set out. Tyre pressure is dictated by vehicle weight. That's why my camper requires higher pressure than a bug. Size of tyre is not relevant. If the pressure is set too high you will be riding on the centre section of the tyre and it will wear faster. If it's too low the reverse happens, you run on the edges and they wear faster.
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Old 18-01-2019, 02:03 PM   #9
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Manufacturers recommend different tyre pressures for different size tyres with the same vehicle weight.
They also recommend different tyre pressures for the same size tyres with different vehicle weights.
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Old 18-01-2019, 02:22 PM   #10
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Manufacturers recommend different tyre pressures for different size tyres with the same vehicle weight.
They also recommend different tyre pressures for the same size tyres with different vehicle weights.
If you won't except my opinion, then fine. Do what you want.
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