Suspension Tire Clearance

[AlanJH]

Recently while laying underneath the rear of my Elan I noticed that the distance between the tire and the lower spring mounts were different. On the right side almost no clearance, but on the left side plenty of clearance. I’m curious if there are any suggestions on where to look to correct the difference.
In full disclosure the car has been modified over the years and has 15” wheels, but I don’t think this would be different with standard wheels.

0384D85A-8575-435E-A719-790E045C1B4F.jpeg (34.3 KiB) Viewed 1200 times

73BD6ECB-D02E-40F9-B220-3E18A2ADCD67.jpeg (42.65 KiB) Viewed 1200 times

[h20hamelan]

Maybe +2 hubs are 0.5 longer than elan?

[berni29]

Hi

I do not think it's possible to tell from those pictures. Well, not for me anyways! I would have to know the truth though, so measuring equipment out!

Berni

[mbell]

You really need to put it in the air take the wheels off and look/measure the position of the components to see if they are offset or not.

It could be narrow wheel bearing in a later issue 18 carrier that should have a wide bearing. But that would also mesd up brake disc alignment.

[CBUEB1771]

This is not unusual. On my +2 with completely standard suspension, wheels and tire size the clearance between the inner wall of the tire and the lower spring platform is about 1/4 inch on one side and a cigarette paper thickness on the other. One thing to consider is that the lower spring platforms are not round. They extend out a bit from the centerline of the strut tube where the end of the spring nests. You may have a situation where the strut tubes are not oriented the same way in the hub carriers. There is no keying in the strut tube or hub carrier to control the rotational position of the tube when installed in the carrier. In your case the difference seems to be greater than I would have anticipated.

[AlanJH]

First an apology for taking so long to follow back up on this, family, work and weather meant I was finally able to take some measurements this weekend.
The clearance from the spring seat to the tire is 0.25” on the left side but only 0.10” on the right. I also measured from the disc to the outside of the hub, 6-7/8” both sides, chassis upright to the outside of the spring base, 7” both sides, and inner cv to the outside of the hub, 17-1/2”.
It does look like the tire has rubbed the spring carrier in the past as the paint finish had been rubbed off, but as the area has old rust and no apparent polishing from the tire.
So even though the tire is very close to the spring carrier it looks like it has been touching in the past but maybe not now.
During the course of measuring I noticed that the drain hole in the spring carrier on the right side was on the outside where as it was on the inside left side, is that normal?

[phil1800]

I have the same situation on my S3. RH clearance of tire and rim is good, but not plenty. LH clearance of tire and rim is very, very little. I expect that the tire will rub the spring platform under brisk driving, although I can‘t see any marks on the tire or platform. This is currently a major fault for my TÜV/ MOT inspector, but I have no clue how to improve the clearance. My Tires and rims are OE knock on‘s. Any clues why the clearance is much different on the rear wheels?

[Donels]

Maybe it’s the wheels. Try changing left to right and see if it changes.

[bitsobrits]

The angle of your two photographs are clearly different, and the perspective change can have an impact on how you see the difference. As noted by others you really need to measure from various points to determine if and where the perceived variance is coming from.

[AlanJH]

Thanks for all the suggestions, It was hard to get representative photos and the measurements were a challenge with very few options to measure from with any kind of accuracy. Impossible for me without jacking up and removing the wheels which I would think changes the geometry, but that’s what I did. I’m definitely going to switch wheels and see if there is a difference. There is always the option of installing narrow springs to increase the clearance and remove the worry.

[berni29]

Hi

I only have experience of plus 2's but when I spoke to Spyder it seems that chassis are jigged using the suspension mounting points. This means that as long as they line up then other parts of the chassis can be pretty much anywhere. I guess the same or worse is true of the standard chassis?

All the best

Berni

[Davidb]

This is a very clever and valuable tool to compare tire/wheel/offset issues:

https://www.wheel-size.com/calc/?wheel1 ... 0mm&sr=0mm

[Andy8421]

This is not unusual. On my +2 with completely standard suspension, wheels and tire size the clearance between the inner wall of the tire and the lower spring platform is about 1/4 inch on one side and a cigarette paper thickness on the other. One thing to consider is that the lower spring platforms are not round. They extend out a bit from the centerline of the strut tube where the end of the spring nests. You may have a situation where the strut tubes are not oriented the same way in the hub carriers. There is no keying in the strut tube or hub carrier to control the rotational position of the tube when installed in the carrier. In your case the difference seems to be greater than I would have anticipated.

The second picture down in this thread clearly illustrates how far out of round the lower spring perch is.

https://lotuselan.net/forums/viewtopic.php?f=19&t=31067&start=

Having the 'bump' adjacent to the tyre vs. having it pointing away from the tyre could explain much of the disparity in clearance being experienced. I had not thought of this before, thanks CBUEB1771 for pointing this out. Well worth checking how your shock tubes have been fitted.