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Author Topic: tyre sizes  (Read 450 times)
matramurena
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« on: October 05, 2021, 10:44:44 pm »

I wonder if there are people here that run on bigger tyres than original and if they have problems with it. Reason for asking is that I am thinking of either have 225/45R16 or 245/45R16 on the back. The 245 would fill the arches pretty nocely but would they bump into the rear-panels? The rims I would like are 9J and therefor 225 would be a little too small. A light stretch. However the same rims in 8J are not available in the right offset and then I would need thick spacers. 

Not easy picking new rims...
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1983 Matra Murena V6 (AR engine)
2003 Matra Avantime 2.0T Expression
2003 Matra Avantime V6 Privilege
Matra_Hans
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Owner of Bagheera, Rancho, Murena & Espace


« Reply #1 on: October 06, 2021, 09:07:04 am »

Hi
I am driving on 205/50 16 and 225/50 16. I think that is the maximuim with standard body panels, the tyres are touching the body under some conditions.
regards Hans
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matramurena
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Posts: 108



« Reply #2 on: October 06, 2021, 10:40:13 am »

Thanx! That setup has an even bigger diameter than what I had planned. Do you have a picture how it looks in the arches?
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1983 Matra Murena V6 (AR engine)
2003 Matra Avantime 2.0T Expression
2003 Matra Avantime V6 Privilege
roy4matra
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« Reply #3 on: October 07, 2021, 12:05:13 pm »

I wonder if there are people here that run on bigger tyres than original and if they have problems with it. Reason for asking is that I am thinking of either have 225/45R16 or 245/45R16 on the back. The 245 would fill the arches pretty nocely but would they bump into the rear-panels? The rims I would like are 9J and therefor 225 would be a little too small. A light stretch. However the same rims in 8J are not available in the right offset and then I would need thick spacers.  

Not easy picking new rims...


Compared to the original Murena 2.2 rear tyres (196/60x14) the 225/45x16 will raise the rear ride height by approx. 10mm and raise the gearing by just over 1 km/hr.  A 225 width tyre will fit comfortably on a 6.5" width or 7" width wheel rim.  Wheel rims should always be narrower than the tyre because its the width between the mounting beads that matter and they come inwards from the sidewalls.  Both a 6.5" and 7" width wheel will fit on the rear of the Murena with a standard offset and should not foul the semi-trailing arm, and the wheel and tyre should not foul the bodywork.  However, please note that the clearance between tyres and semi-trailing arm or tyres and bodywork will be less under cornering than measured when the car is static as things move.

A 245 width tyre will fit on a 7.5" wheel but now the wheel and tyre will foul the semi-trailing arm if the offset is standard (29mm), so you will need a smaller offset* than standard to move the wheel outwards away from the arm.  But if you keep the change small - say around 15mm, you would need an offset on the new wheel around 15mm and that should be enough to keep the wheel and tyre away from the semi-trailing arm and probably still not foul the bodywork - although I haven't checked this so you would need verify that for yourself.  Also note that once you change the offset the wheel bearing gets a twist torque loading which can reduce its life.

The tyre required for a 9" wide wheel rim would be 275mm or wider and I don't think you should be trying to fit that wide a wheel or tyre on the Murena, nor should something that big be necessary!  Also the offset would have to be even less to clear the semi-trailing arm, and then the outer edge of the wheel and tyre are bound to foul the bodywork.

*N.B. please understand that the larger the offset of a wheel, the more it mounts inwards and the smaller the offset the further out the wheel mounts, because the mounting face on the hub does not alter.  Many people originally get this the wrong way around.

Roy
« Last Edit: October 07, 2021, 12:27:58 pm by roy4matra » Logged

matramurena
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Posts: 108



« Reply #4 on: October 08, 2021, 12:35:05 pm »

According to all tyremanufacturers 245 or 255 is the right size for a 9J rim. 235 and 265 are possible but not optimal.

I need to get the wheels out by 5 cm because of the Fleischmann F3 kit, thats the reason for a change of wheels.
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1983 Matra Murena V6 (AR engine)
2003 Matra Avantime 2.0T Expression
2003 Matra Avantime V6 Privilege
GP
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Posts: 297



« Reply #5 on: October 10, 2021, 08:07:45 am »

According to all tyremanufacturers 245 or 255 is the right size for a 9J rim. 235 and 265 are possible but not optimal.

I need to get the wheels out by 5 cm because of the Fleischmann F3 kit, thats the reason for a change of wheels.

That is very interesting a Fleischmann F3 Kit. I recently prepared/translated  an article from an old German Sportcar Magazine on this very car for the Matra Enthusiast Club in the U.K.  Unfortunately it seems we currently have no Club Editor or even a Magazine anymore which is a shame.  Cry

Anyway here is the article below. Only used Google Translate, so it is quite strange English.

If you would like the actual magazine send me a private message with your address and you have an early Christmas present!

Cheers,

Graham

P.S. I had the start of one of these projects many years ago. Unfortunately it failed! I actually do have these wheels still although they are in need of a refurbishment/repair.
« Last Edit: October 10, 2021, 08:50:17 am by GP » Logged
matramurena
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Posts: 108



« Reply #6 on: October 11, 2021, 08:15:42 pm »

That last pic looks sad...  Shocked
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1983 Matra Murena V6 (AR engine)
2003 Matra Avantime 2.0T Expression
2003 Matra Avantime V6 Privilege
Grapes
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Posts: 121


« Reply #7 on: October 12, 2021, 04:10:42 pm »

I used to drive: Rear = 225/40ZR16 Front = 205/45ZR16
Roy told me that messed the whole car up making the nose sit higher than the rear although I didn't notice it. Later I read some of the 1.6 had the rear too high anyway from the factory and someone had rigorously adjusted the torsion bars on my car as well so that might have levelled it all out but I wouldn't be surprised if it didn't.

Anyway I think 225/45 will fit the rear but I'm currently driving 14" with much higher walls and it's tons more comfortable... too comfortable actually so I do in fact want to switch to 15" and have a little stiffer ride but I wouldn't want to go back to the setup I had.

My rear was 225/40 instead of 225/45 you are planning so there was more space... Not sure how big the difference is. By the way, my French aint great but I think Politecnic even sells 17": http://www.politecnic.com/roues.htm

I would like to get a wide body on mine at some point. I wonder if its possible to mix and match kits...
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