MatraSport Forum

Each model => Bagheera => Topic started by: Lanng on July 26, 2012, 10:32:20 am



Title: Newbie question - wheel/rim size
Post by: Lanng on July 26, 2012, 10:32:20 am
I was wondering what the max size of wheels that can be mounted on the Bagheera?

What bolt patterne? Can i 4x100 with special nuts?
What is the bolt pattern ET and Center for the Bagheera?
Is 15" the biggest size to be used on the Bagheera?
And how wide tieres can be mounted on the Bagheera?

Best regards
Jacob


Title: Re: Newbie question - wheel/rim size
Post by: bert1 on July 26, 2012, 03:36:22 pm
Hi Jacob.

The Bagheera hubs are 4X98 like Fiats, Alfas and Lancias. Some people use "wobble bolts" to mount 4X100 wheels on 4X98 hubs. I like my wheels to stay on and don't recommend such devices. A bit like screw-in wheel studs - many people use them for many years and have no problem with them even though they are an engineering compromise. Knowing my automotive luck the wheels would fall off before I made it around the corner.

The hub-centric diameter of the Matra hubs is 58mm - like an X1/9. Using other Fiat wheels with 59mm will mean that the bolts will be required to centre the wheel which is not ideal - but given the miniscule difference probably acceptable. You would need to be careful to centre the wheel when mounting it.

I am unsure of the original ET (offset) of the Bagheera wheels but could check for you.

The rear of a Bagheera is very generous. For a laugh I put one of my racing wheels on the back - and even at 15X8 (ET +4mm) and Dunlop slicks in 220/565/15 there was plenty of room. It looked FAT!

The front is much more difficult. 5.5" rims are about the max - you MIGHT be able to squeeze to 6.0" rims if you keep a low offset

Recently I dragged out a set of wheels that I use semi-slick tyres on my Fiat racecar. They are Maserati 14X6.5 ET10. As you can see below the 205/65/14's fit EASILY on the rear. The 185/55/14's DON'T go close at the front. Trouble is that I have now decided that I love the look of these and they MUST be made to work - so  I have ordered a pair of 14X6's and will modify the guard as needed.

(http://i648.photobucket.com/albums/uu209/franken_bert/Bagheera/P3240033.jpg)
(http://i648.photobucket.com/albums/uu209/franken_bert/Bagheera/P3240037.jpg)


Title: Re: Newbie question - wheel/rim size
Post by: valross on July 26, 2012, 04:59:29 pm
Hi,

The original tyres on my 1980 Talbot Matra Bagheera X were Michelin XVS 205/70-HR13 rear and 175/70-HR13 front. These tyres - if you can find them - cost a fortune. So I had spacers made to fit the 14" Alfa-rims to get the right off-set and I bought Michelin MXV 195/65-HR14 rear and 175/65-HR14 front. These tyres have the same circumference as the originals.
Hub centre on front hubs are 58 mm, on rear hubs 55 mm. The spacers are 10 mm thick. Bolt circle 4x98 mm.

(http://www.ordsak.se/Bilder%20Matra/Sida.jpg)

(http://www.ordsak.se/Bilder%20Matra/Spacer.jpg)


Title: Re: Newbie question - wheel/rim size
Post by: bert1 on July 27, 2012, 03:42:36 pm
Interesting that the tyre size changed on the 1980. Valross are you sure they are original?

My 1977 had 155HR13 front and 185HR13 rear Michelin XAS (steel wheels - my car is a NON-S/X). I believe these "full" profile tyre sizes are actually 82 profile.

Using 14" equivalents gives me 185/60/14 front and 215/60/14 rears as (almost) exactly the same diameter. Sadly tyres in these sizes are impossible to source - in my country at least. I will need to investigate importing MXV's in your sizes Valross. The rear is slightly smaller overall but the shorter gearing will not be a problem with our ridiculous 110km/h maximum speed limits.

I will also need to double check the hub-centric diameter at 55mm for the rear. Either they changed on the later cars or I was lazy and didn't bother measuring it when I found the front at 58mm to be the same as my Fiat!

PS the Alfa wheels look good on the car too - these are Alfetta or 90? What width?


Title: Re: Newbie question - wheel/rim size
Post by: Spyros on July 28, 2012, 04:20:13 pm
Interesting that the tyre size changed on the 1980. Valross are you sure they are original?

Yes.

The size are about the same


Title: Re: Newbie question - wheel/rim size
Post by: valross on July 28, 2012, 06:43:46 pm
Interesting that the tyre size changed on the 1980. Valross are you sure they are original?

Yes. According to Revue Technique Automobile, the Bagheera X was equipped with bi-colored alloy rims (silver /black or gold / black) with 175/70x13HR front and 205/70x13HR rear from July 1979.

My Alfa rims are 5" wide. They came from an Alfa 33 Quadrifoglio.


Title: Re: Newbie question - wheel/rim size
Post by: andyowl on July 30, 2012, 05:32:04 pm
Check the pictures of "Bagheera Roll cage wanted" to see my original Bagheera alloy wheels.

Reply #26 I think.

Andy


Title: Re: Newbie question - wheel/rim size
Post by: andyowl on July 30, 2012, 05:38:30 pm
Around the same reply in "Roll cage wanted" is discussion of tyre sizes.
Example..

I have also ordered some "sticky" tyres from Yokohama - the A048-R. They will go on original Bagheera alloy wheels which had 175/70 and 205/70 tyres as an option (my Reparation guide tells me).

I couldn't find any tyres of the right size that were within the approved MSA/FIA tyre list. So I have ordered 175/60 R13 and 205/60 R13. Slightly lower gearing for Sprints and Hill Climbs may give some advantage even if they will not look quite right.

Andy


Title: Re: Newbie question - wheel/rim size
Post by: bert1 on July 31, 2012, 05:26:23 am
Andy were you able to get the "M" compound A048's? I've had a lot of success with the "M"'s but the "S" compound has given the A048 a shocking reputation (in Australia at least - I guess track temperatures would be warmer) for only lasting a few heat cycles and then going to pieces.

Sorry for the hijack Lanng!


Title: Re: Newbie question - wheel/rim size
Post by: andyowl on July 31, 2012, 09:15:55 pm
I did not know about "M" and "S" rubber compounds when I ordered the tyres. I received "S" for the rear and "M" for the front.

If "S" are the more grippy I certainly need them that way at the rear. More grip at the front would help to reduce the understeer but increase the tendency to spin perhaps? In the UK and in my Sprints and Hill Climbs the tyres do not get warm enough to damage the "S" compounds?

I checked all four tyres this morning to note the M or S details and all four still look OK for my level of motorsport. What I lack is skill, and since my crash at Crystal Palace last year, more confidence!

In another message today I write that Baggy Joe now has a working Wade Supercharger with the old 2" (50mm) SU carburettor. The 78% increase in boost pressure feels good. Now to learn how to control that too!

Andy


Title: Re: Newbie question - wheel/rim size
Post by: Lanng on March 23, 2013, 08:51:06 am
God morning.

I never found the ET for the Bagheera - does some one have that number?

best regards
Lanng


Title: Re: Newbie question - wheel/rim size
Post by: mimu on November 29, 2013, 01:11:26 am
Pretty new with Bagheeras.
I have two set of original 13" alu wheels in my garage, if I'm not totally wrong the ET is on the wheel.
Next time I'm down there I will take look and may be some photo.


Title: Re: Newbie question - wheel/rim size
Post by: andyowl on November 30, 2013, 09:14:31 am

I never found the ET for the Bagheera - does some one have that number?

Sorry - what does "ET" stand for? What do you need?

Andy


Title: Re: Newbie question - wheel/rim size
Post by: Matra_Hans on December 02, 2013, 07:46:12 pm
Hi Andy. ET is the short form of the German word 'Einpresstiefe' which literally translates as 'insertion depth' but I think that the normal  English term is offset.

Hans


Title: Re: Newbie question - wheel/rim size
Post by: andyowl on December 03, 2013, 07:54:16 am
Clarification please...
I'm asking:

Is "Offset" the distance between the face of the flange where the wheel is bolted and the centre line of the wheel rim?

If so I can measure it easily.

Andy


Title: Re: Newbie question - wheel/rim size
Post by: roy4matra on December 07, 2013, 10:30:02 pm
Clarification please...
I'm asking:

Is "Offset" the distance between the face of the flange where the wheel is bolted and the centre line of the wheel rim?

If so I can measure it easily.

Andy

Yes it is Andy.  Even the RT manual does not give the offset or ET figure, but since the front suspension is very similar to the Murena where the correct offset is 29mm, I suspect it will not be much different.  As someone else (mimu?) stated, alloy wheels normally have the figures cast or stamped in them, so check your original alloys.

Roy


Title: Re: Newbie question - wheel/rim size
Post by: mimu on December 20, 2013, 08:21:09 pm
Where in the garage last night, numbers which I thought was ET was just sizes.
So some research to do.
tbc


Title: Re: Newbie question - wheel/rim size
Post by: GP on December 20, 2013, 09:53:05 pm
Something of interest E.T. / Wheel  Offset calculator

http://www.oponeo.co.uk/advice-and-tips/wheel-offset-calculator


Title: Re: Newbie question - wheel/rim size
Post by: mimu on February 11, 2014, 11:33:41 pm
Here is a simple guide how to calculate the ET:
http://forum.jdmstyletuning.com/showthread.php?20793-How-To-Measure-OFFSET-on-your-Rims

I will of course measure my wheel next time I'm in the 'cave'


Title: Re: Newbie question - wheel/rim size
Post by: roy4matra on February 15, 2014, 08:37:24 pm
Something of interest E.T. / Wheel  Offset calculator

http://www.oponeo.co.uk/advice-and-tips/wheel-offset-calculator

Whilst this is a useful little on-line wheel calculation tool, it suggests that it is perfectly alright to go changing the offset as long as you can fit the wheel within the body or it won't stick out too far.  The whole purpose of the wheel offset it to keep the centre line of the wheel aligned with the centre line of the wheel bearings in the hub.  If you change the offset, you put a torque loading on the bearings which they were not designed for, and they will wear and fail prematurely.

The calculator is quite useful as it shows the displacement of the centre line as you alter the offset.

The aim when fitting different wheels is to keep the offset the same or very close to the original to minimise the twist effect on the bearings.  On a car with easily replaceable wheel bearings, I suppose it would not matter quite as much since they could be replaced regularly; but on a Bagheera or Murena where they are a big job to replace you really should not be changing the offset.

Roy