2 replies to this topic

[Yams]

Hey guys. 

I just wanted to check that I have all my numbers right. I have an 1986 244 with standard steels. I have done my calculations based off the info that the steel wheels are 5.5x14 et20. I'm hoping that this is right or the rest is possibly worthless!

I am wanting to fit a set of staggered Porsche 928 7 slots. The fronts are 7x16 et65. The rears are 8x16 et52.

 

 

 

I just wanted to run some of my figures by you guys, as I know some of you on here are quite into your Motorsport engineering and such.

Rears:

I've measured the room I have between the inner rim of my rear wheels and the nearest point of contact, which is the suspension spring. I have just over 30mm it seems, if not a little more. 

the offset being so high on the porsche wheels means that if they bolted straight on, the inner rim would be 63mm closer to the spring than the steels (Not possible because there is only around 30mm of clearance stock). Being as wide as they are, if they bolted straight on the outer rim would be in almost exactly the same place as the stock steels. I've measured the outer lip to the wheel arch and there is quite a bit of room to allow for poke before it becomes legally questionable, I would say around 60mm. 

If I fit a 45mm adapter this would essentially reduce the wheel wheel offset on the rear to et7. This would then mean the inner rim is 18.8mm closer to the closest point of contact (spring), giving me in theory about 11mm clearance. The outer rim will then be protruding 44.8mm further out than the stock steel wheels. According to my measurements this is 'ok' but should I want to lower the rear at all the arches will have to be rolled for compensate for this. 

Fronts:

 

Again, on the front i have just over 30mm clearance between the inner rim of the steel wheel and the suspension strut. if the porsche wheels bolted straight on the inner rim would be 64mm closer to the strut over the steel wheels (again not possible since there's only 30mm there anyway) and the outer rim would be inset by 26mm over standard set-up. on full lock in either direction i've got about 25mm of clearance between the wheel and the strut.  

If i fit a 45mm adapter it will bring the offset down to et20. this means the inner rim will be 19.1mm closer to the suspension strut over stock, in theory giving me just a hair under 11mm clearance, and 6mm on full lock, and the outer rim will poke 19.1mm more. 

Before I fit these wheels I will be replacing the front ball joints and track rod ends, as it seems they haven't been replaced in the 30 odd years its been on the road. I'll also be using billet aluminium adapters from SuperForma, so they should be light and strong. They make sizes up to 60mm so i'm going to assume that 45mm isn't too extreme. 


I just wanted to see if you guys think that's enough clearance, and that I've done my maths correctly!

many thanks, sorry it's a bit of a wall of text.

Yams

Edited by Yams, 12 April 2016 - 04:19 PM.

[nicklouse]

http://www.willtheyfit.com

Put the info in and play with the ET it will hive you a good way of looking at it. You can also (need to) add the tyre sizes.

As to the actual spacers. Hub centric ones made of steel bolted to the hub and wheels to the adaptor.

Might cost a little more but.

[Yams]

As stated I'm going to use adapters made of billet aluminium as i think steel would be heavy (centre bore of hub to centre bore to wheel etc), as the PCD of the porsche wheels is different to the volvo hubs. With my figures it all makes sense on paper, and translates well to willtheyfit.

 

however I was also concerned with fitting a 45mm adapter to the hub, and to whether it would have any adverse effects on the car, like cornering, accelerating and braking, and whether or not the clearance I have given myself from the suspension is enough? Also will having lighter adapters help in any way other than weighing less? Would the the rolling resistance difference be noticeable?

Edited by Yams, 12 April 2016 - 06:59 PM.