Author Topic: Front riding high after changing knuckles  (Read 2472 times)

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Guldbergdk

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Front riding high after changing knuckles
« on: July 29, 2019, 03:29:54 PM »
Hi

I have an issue, that after chainging the knulckles (with discbrakes attached) that the front is riding a lot heigher than before. Something like 5-10cm. I also changed the dampers, but I tried to put it on the ground without and the result is the same.

After a small test drive I noticed that one of the leafspring block were cracking, so I changed the leafspring, block and clamps as well. Tigthtning the leafspring to almost horisontal before mounting it (by using a M10 rod in place of the damper and lifting it up). Upper A-bar as well as all tierods and steering damper is also changed.

Another curious thing.

The steering is horrible (un-driveable), but I guess thats because the angles are all messed up.

I guess there is at least two options to why the heigh is all wrong
1. The new knuckle has a different height from the leafspring bolt to the axle center. This is the new knuckle
2. The new spring is to stiff/not tensioned enough (im pretty sure that the height was the same before the new spring was fitted).

I guess I could resolve it by mounting a lowered spring/lower blocks, but I want to find the culprite first

Any help would be greatly appreciated. Maybe somebody could measure the distance like in the picture here (I get mine to 90mm). As well as the distance from the leafspring bolt to the ground facing to the front of the car. (Mine is 175-180mm)


Guldbergdk

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Re: Front riding high after changing knuckles
« Reply #1 on: July 29, 2019, 03:52:07 PM »
More pic

Pete126

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Re: Front riding high after changing knuckles
« Reply #2 on: July 30, 2019, 01:41:00 AM »
When you changed the front spring or disassemble anything on the front suspension you need to get the suspension tracked up, when you tighten the front eyelets on the leaf spring you need to do this with the car resting on its wheels, I had a similar problem when I changed my front spring, took it to a tyre shop and they adjusted the front tracking, after it drove like a different car it also lowered the front end, was allot smoother and didn't bounce all over the road
Pete.      il cavallo piccolo

Guldbergdk

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Re: Front riding high after changing knuckles
« Reply #3 on: July 30, 2019, 07:52:02 AM »
I do plan on having it tracked on all four wheels, I just want to fix the heigh issue first.

On your suggestion I tried to loosen the leafspring and upper A arm bolt while on the ground and bounce it around a bit. It didnt do much though. I remember reading in the workshop manual that when installed the knuckles are pre-mounted on a 95 degree angle to the spring. I also read that when pretensioned, the center of the bolt hole should be only 28mm from the flat of the spring. Seems like a lot, but I might have to try and pretension the hole thing one more time and tighten the leafspring and A-arm while its all tensioned up.

Another question though: The new knuckles didnt really fit that well on the old A arm and spring. There were a gap between the top of the knuckle and the A arm. And I couldnt fit a new bushing in the spring, the hole was like 2mm smaller than the bushing. Im pretty sure its not a 1. series (they had split A-arms I recall), but could there be something wierd going on here? or are all models the same regarding springs/knuckles from 2. series and forward.

Guldbergdk

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Re: Front riding high after changing knuckles
« Reply #4 on: July 30, 2019, 10:42:07 AM »
Could somebody measure the distance from the center of the wheelhub to the top of the wheel arc at the angle of the shock absorber? I get mine to 33 cm on one side and 34 on the other side.

I redid the spring tensioning and pulled it to 28mm before tightning the leafspring clamps. It helped, but it still seems to ride heigher than before. I might have to try and flatten it even more. It looks like its suppose to be 28mm just by static weight (thus after the tension is released. Its the Y in the attached pic.


ChrisRLewis

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Re: Front riding high after changing knuckles
« Reply #5 on: July 30, 2019, 11:26:19 AM »
If I remember correctly I had two separate sets of knuckles which were of a slightly different dimension in sizes, so there maybe differences depending on the model year? Have you measured the old knuckles with the new ones?

Guldbergdk

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Re: Front riding high after changing knuckles
« Reply #6 on: July 30, 2019, 11:31:04 AM »
I had to cut them off with the angle grinder. Not anticipating that I would need them the went in the trash:)

I do think Its a leaf spring issue though. The workshop manual says that the height from the bottom of the leaf spring clamp to Ground should be 170. Mine is around 190. I’ll try and tension the spring again again

1973/126

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Re: Front riding high after changing knuckles
« Reply #7 on: July 31, 2019, 09:30:00 AM »
 Did you change both the leaf spring blocks? I'm only asking as some of the early cars had slightly lower blocks, so this could make it more uneven side to side.
 The new leaf spring will also need a bit of time to settle. You've got to think the old one had 40 years of use so would be much more flat.
 
 If you want to reduce the height you can lower the alloy blocks. Just make sure they are machined even, or you can flip one of the leafs to make the spring more flat.
1972 Fiat 500
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michaelodonnell500

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Re: Front riding high after changing knuckles
« Reply #8 on: July 31, 2019, 01:53:59 PM »
I had a similar issue when I rebuilt the front of the car.
Everything was bolted together correctly,  but the ride height was ridiculous. The spring was the issue in my case. I put a bag of sand in the front of the car and continued to drive it. 2 weeks later the front spring had settled to a normal height. I probably overlooked something when I rebuilt it, but the bag of sand sorted it for me.
Rust does not discriminate

Guldbergdk

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Re: Front riding high after changing knuckles
« Reply #9 on: July 31, 2019, 02:21:53 PM »
Ha. I like that idea.

What I want to try now:
1. Tighten it up again (again again)
2. Shim the mounting blocks or add a 2mm piece of rubber in the leaf spring bow to increase holding pressure. (Probably the ladder, so I can remove later if needed).
3. Add some bags of sand to the front:)

One question though, should I wait to have it tracked until after the spring settles?

michaelodonnell500

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Re: Front riding high after changing knuckles
« Reply #10 on: August 01, 2019, 10:35:02 AM »
you can do the tracking now, but it won't solve the handling issue until the ride height is sorted, then the tracking will need to be done again anyway!
You can do the tracking at home with string and axle stands. PM me if you want some details on this.

You could try -
1. Park it on ramps (level)
2. slacken every suspension bolt.
3. Add weight to the front until the ride height is good.
4. Tighten up the bolts

I wouldn't recommend adding a shim. You shouldn't be adding extra things. You already have a fault, don't try to fix it by adding another variable!
Rust does not discriminate

Guldbergdk

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Re: Front riding high after changing knuckles
« Reply #11 on: August 01, 2019, 12:09:29 PM »
Ill try the sandbag method adding some weight to the front for the firs couple of weeks.

I did the 1-4, but with threaded rods in place of shock absorbers pulling the leaf spring all the way to horizontal before tightning. The issue is that when releasing the tension it springs back like 5cm.

Toe in is a easy set with long aluminium level on the front tyre aiming for the back tire. Its more that the camber is ridicules when the ride is so heigh. Something like 5degrees. I looks like a cartoon car with the wheels angled so much:)

1973/126

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Re: Front riding high after changing knuckles
« Reply #12 on: August 01, 2019, 12:33:51 PM »
 If you want a quick fix to the height issue you can lower these blocks. It will make a bit of a difference.
 After that follow the advice above.
1972 Fiat 500
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Guldbergdk

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Re: Front riding high after changing knuckles
« Reply #13 on: August 04, 2019, 03:55:02 PM »
Didnt have any sandbags:) 

It helped alot and ill probably leave it there for a couple of weeks. Main issue now is that one side is 3 cm heigher than the other. I'll try and adjust it again and maybe flip the spring around.

But for anyone experiencing the same issue:
1. Tension the spring to horisontal using threaded rods in place of shock absorbers
2. Clamp the spring and tighten the bolts
3. Fill the trunk with sand or rocks

Hopefully the stones are not a permanent thing:)

DEYAN IYI

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Re: Front riding high after changing knuckles
« Reply #14 on: August 05, 2019, 10:26:50 AM »
You can diy something like: