Chaz
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 posted on 26/2/26 at 08:13 PM |
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Rear lower wishbone / upright lateral play – bolt & crush tube clearance?
Hi All,
Hopefully someone can help!
I’ve got an MK Indy 2004 and I’m trying to diagnose some lateral movement at the rear hub.
With the car jacked up, if I hold the rear wheel at 3 and 9 o’clock and push/pull side to side, I can feel noticeable movement. It’s not a wheel
bearing knock — the entire upright (bottom part) is shifting slightly relative to the lower wishbone.
I’ve traced it to the bottom upright-to-wishbone bolt. The long bolt that runs through the lower wishbone and through the bottom of the rear upright
appears to have clearance where it passes through the metal crush tube inside the bush.
Both sides are the same.
The car hasn’t done much mileage, definitely not wear. It feels more like clearance between:
• Bolt OD
• Crush tube ID
When tightened fully, the joint is clamped, but there’s still perceptible lateral play at the hub when levering the wheel side-to-side.
It doesn’t feel like bush deflection — it feels like the bolt is moving inside the sleeve.
Questions:
1. Should this joint be zero-clearance between bolt and crush tube?
2. Are MK Indys typically M12 here, or 1/2”?
3. Has anyone seen metric/imperial mismatch causing this?
4. Is crush tube length vs bracket spacing a common issue on these?
I’m trying to avoid bodging it and want to fix it correctly. The concern is dynamic toe change under braking/acceleration if there’s any slop in that
lower pivot.
Any advice from those who’ve rebuilt these joints properly would be appreciated.
Thanks 👍
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coyoteboy
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| posted on 26/2/26 at 08:40 PM |
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The crush tube should be clamped in place in the bracket; neither the bolt in the tube, nor the bolt in the bracket need to be 1:1.
Sounds like insufficient clamp force or too short a tube.
Haven't watched it all the way thru, but this might help https://www.youtube.com/watch?v=8Ex0dGojHZI
[Edited on 26/2/2026 by coyoteboy]
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Sanzomat
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| posted on 26/2/26 at 09:29 PM |
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I've just replaced the front bushes on my Locost which uses MK indy wishbones and bushes. The crush tubes have a 1/2" ID which is a nice
(not tight) fit on a 1/2" imperial bolt. I believe MK did use 12mm bolts back in the day so there will be a bit of additional clearance - 12mm vs
12.7mm. If you have any 1/2" bolts lying around might be worth trying one to see if it cures it. However, the crush tube should be clamped tight
in the clevis so the bolt clearance shouldn't technically be a problem.
[Edited on 26/2/26 by Sanzomat]
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Chaz
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| posted on 26/2/26 at 10:49 PM |
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Thanks both — that’s helpful.
I think I need to clarify which part I’m referring to.
I’m not talking about the short crush tube inside the wishbone bush itself. That one seems fine.
I’m referring to the long steel crush tube inside the rear upright (the one the long lower bolt passes through). It’s quite long (circa 100–120mm) and
appears to have noticeably more clearance on the bolt than the wishbone bush tubes.
When I insert the current bolt (which I believe is M12), there seems to be significantly more movement inside the upright tube than in the wishbone
bush sleeves.
So effectively:
Bolt → wishbone bush sleeve = reasonable fit
Bolt → upright crush tube = noticeable clearance
That’s why I’m questioning whether there’s a 12mm vs 1/2” mismatch specifically at the upright rather than at the wishbone bush.
I fully understand that in theory the crush tube should be clamped solid between the clevis brackets and the bolt-to-tube clearance shouldn’t matter
once torqued. However, with the bolt fully tight, I can still feel lateral hub movement at 3 and 9 o’clock, which feels like the upright pivoting
slightly on the lower bolt.
So I’m wondering:
• Did MK use 1/2” ID tubes in the upright but 12mm bolts?
• Is it common for the upright tube to be imperial while the supplied bolt was metric?
• Has anyone measured the ID of the upright tube specifically?
Before I start changing hardware I’d like to confirm what the correct bolt size should be for the upright tube, not just the wishbone bushes.
I’ll probably just take all apart, measure and go from there 👍🏻
Appreciate the input 👍
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Sanzomat
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| posted on 27/2/26 at 07:54 AM |
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I see now. In my experience buying steel tube it is usually made in imperial sizes. Normally described by OD and wall thickness. E.g the wishbone bush
crush tubes are 3/4" OD with 1/8" wall thickness thus 1/2" ID. As such it is quite likely the upright crush tube is also imperial and
the closest metric bolt may well have been used as imperial bolts (particularly long ones) are unpopular (and therefore rare and expensive) in the UK.
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Chaz
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| posted on 27/2/26 at 08:01 AM |
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Sanzomat thank you 🙏🏼 👍🏻😊
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Slimy38
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| posted on 27/2/26 at 08:10 AM |
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While I use an MX5 upright rather than an Indy, I think it's similar to how the Indy upright is designed so hopefully I'm keeping up with
what's going on. The clamping principle still applies though, just in this case it should be a series of crush tubes that are all clamped
together, rather than a crush tube clamped between a bracket.
I was also wondering whether there are any tell tale marks on the side of the upright? If it was moving in relation to the clamping surfaces would it
remove a layer of paint?
One more thing is whether the bolt is solid or threaded as it passes through the upright, and that's making a small problem even worse?
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jacko
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| posted on 27/2/26 at 07:10 PM |
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Hi my Indy was a 2004 made car and I am 95% certain the bolts where 1/2 ins imperial
It’s so long ago to remember
G
555
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adithorp
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| posted on 1/3/26 at 11:52 AM |
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The bolt should be tight and once it is there should be no movement possible in the crush tube/upright tube. If it truly is tight then the only
possibilities i can see are...
1. The play is actually in the bushes.
2. The nut is tightening against the bottom of the bolts thread/shank and not actually clamping the tubes/upright. Try an extra washer or 2 under the
nut to rule that out.
I guess if the bushed crush tubes were too short, then it could ve the brackets aren't squeezing down onto them but they'd have to be way
too short.
The issue with 12mmbolts in ½" holes is that when you tighten them the bolt can be positioned differently in the hole and vary the geometry
slightly. Once tight it can't move.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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Chaz
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| posted on 2/3/26 at 08:54 PM |
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Thanks, everyone for the replies. I’ve taken out the bolt and remeasured the crust tubes and they all seem to be 12.2mm so not enough to fit at 1/2
inch (12.7mm) through. I don’t have a half inch bolt but I suppose the acid test is to buy one and see if it fits.
Appreciate the comments about adding in more washers etc. Bushes have only done 2500miles, not those.
Thanks again to everyone here!
The knowledge base here still surpassing ChatGPT hah!
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