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Where to put the eccentric bolt?

Motorsport Wheel Alignment Fundamentals

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Front knuckle/hub (or whatever you call it, I'm talking about the part that connect to the strut) have two bolt holes. Do I put the eccentric bolt on the top hole or the bottom hole?

Can I put 2 eccentric bolts, one on each hole?

This is where the hub bolts to the lower strut? What vehicle is it - it should specify where it goes, if not, I would expect the top one - if one is slotted, use it. With some vehicles, I expect you can use two bolts.

What do you mean by slotted?

What kind of car use 2 eccentric bolts?

slot definition: 1. a long, narrow hole

Any vehicle that uses them, I would not expect it to be a common thing.

Your initial post would have been much more useful if you had specified the actual vehicle - perhaps if you added it?

Okay first of all, I always put eccentric bolt in the upper hole. That's the way I've been taught, the way I seen everybody do, and the way I've always used.

Then I watched Andre said in eccentric bolt module, that "an eccentric bolt is useful to replace one of the bolts holding the strut and hub" or something like that. Maybe I'm over analyzing what he's saying, but he didn't said the top bolt. So I think he implies that it can be installed on either hole to provide camber adjustment.

I try to imagine putting an eccentric bolt in the lower hole, and I don't think it'll work, since the top bolt and lower control arm ball joint provide a fixed position for the hub, so I think the only thing that might move is the strut angle relative to vertical line.

Then I watched a youtube video that explains sometimes tire shop will install 2 eccentric bolts, one in each hole, if 1 bolt is not enough to provide the range of adjustment needed. The youtuber is a DIYer (and honestly I'm not even sure if he know what he's doing). So here I am, looking for an educated answer.

Another question, if my imagination about using an eccentric bolt in lower hole is correct in that it won't affect camber and only affects strut angle relative to vertical, will it change the KPI? My guess is it won't, but I will appreciate a second opinion.

I don't recall one being used in the bottom attaching hole, just the top - but I'm not saying it couldn't be done, but the more common practice would be to extend the slot slightly if there isn't enough adjustment available.

I think you may be a bit confused - the reason there is the adjustment at the bolt(s) is to correct the camber - the tilt of the wheel - as there may be manufacturing tolerances of the hub and/or strut. While there will be potential for a very small alteration of the upper strut assembly, the top mounting point, and the track control arm and it's joints, will still be in exactly the same place, so there will be no change in KPI. Well, if there is a minor alteration in ride height, there is potential for an extremely small variation, just as there is for the scrub radius as the angle of the wheel assembly changes slightly in relation to the lower joint, but they are well down the list of concerns.

In theory, you could put eccentric bolts in either or both of the holes in the lower part of the strut, the end effect (adjusting the camber) is very similar.

It will depend on which holes you can fit the eccentric bolts into, which will also depend on the style of the eccentric bolt you're using. Normally, the hole that is slotted is the one that's designed to take the eccentric bolt, as is shown in the top hole in the picture below. You also have the potential of slotting the other hole if you need more camber correction. 😃

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Oh so that's the slot Gord was referring to! I've never seen a bolt hole like that, sorry for my lack of experience.

The type of eccentric bolt I've experienced with is shown below. I use them on stock strut to provide camber adjustment.

Attached Files

No problem Hairul, we're all here to learn!

You will often see one of the holes in a MacPherson strut be slotted like this. This slot is added to allow you to use a full size offset bolt, I have added an example of this below. You can see how this style of bolt has the full diameter which is quite different to the image you posted. You can see how this full width bolt is a better option and would be much stronger than the example you showed. The issue with the full width bolt is that you need a slotted hole to fit it in!