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Floating VW Samba Member
Joined: April 28, 2015 Posts: 1597 Location: The South Zone
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Posted: Mon Sep 20, 2021 2:20 pm Post subject: Re: Shimmy While Braking After Installing New Wheels |
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Oh, and definitely keep an eye on your scrub radius. A little bit of scrub can be a good thing, but too much can cause the difficulties described by Mrgoodtunes above. Somewhere around 4 cm is probably good.
When I converted my drums to discs, it kicked the scrub radius out to about 6.3 cm. I feel this much scrub improved stability, especially in the corners, but also made the steering feel a touch heavy and prone to bump steer when the suspension was loaded. It was a fair trade, but only just.
I imagine those 25mm adapters and rims will add a considerable amount of scrub, which might be tolerable now, but if you ever upgrade to discs, you might not be happy with the result. _________________ "It's time you started treating people as individuals, rather than mathematically predictable members of an aggregate set, regardless of how well that works." |
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Starbucket Samba Member
Joined: April 30, 2007 Posts: 4026 Location: WA
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Posted: Mon Sep 20, 2021 3:35 pm Post subject: Re: Shimmy While Braking After Installing New Wheels |
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It's because the front end is so light, When I put 8 spoke mags with 70 series tires on my 78 vert I had the same problems and cured it by putting two bags of cement (still in the bag ) in the front. |
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Franco1962 Samba Member
Joined: October 23, 2017 Posts: 8 Location: Mass
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Posted: Mon Sep 20, 2021 8:12 pm Post subject: Re: Shimmy While Braking After Installing New Wheels |
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That痴 too funny. After watching a video on aircooled.net I知 going to try to replace the control arm and sway bar bushings with urethane bushings. As I mentioned before a friend said that under breaking the car will have different characteristics. I知 wondering if changing those bushings will keep the steering Geometry in tact and keep it from shuttering. I ordered a kit for about 50 bucks so I think I might give that a shot first as it doesn稚 seem too terribly invasive. I値l certainly report my results back to the form and if anybody else has any better suggestions I知 all ears. Thanks for all your thoughts and advice.
Frank |
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MrGoodtunes Samba Member
Joined: May 14, 2012 Posts: 852 Location: South Florida
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Posted: Sat Sep 25, 2021 1:00 pm Post subject: Re: Shimmy While Braking After Installing New Wheels |
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Franco1962 wrote: |
... After watching a video on aircooled.net I知 going to try to replace ... bushings ... |
Is that the Super Beetle "death wobble" video? Maybe you'll be lucky and that fix will solve your brake shimmy. But like your BMW buddy says, alignment issues are very different for braking from what they are when just cruising. Maybe you need a video of your own situation. That's what I tried to do when I had a brake judder problem. It was too much to set up a camera that records while braking. So I just recorded what's happening at various suspicious locations while wiggling front left wheel with my left hand at 9:00 on the tire, right at 3:00 (pushing with one hand while pulling with the other). For example, here's looking at inner tie rod ends:
https://youtu.be/BMNcRvyuXQU
My brake judder turn'd out to be caused by shiddy sidewalls on Firestone tires back 10~12 years ago when they were in the news due to problems on Ford Explorers. And now with completely different tires, brake judder is sneeking back. Replaced left outer tie rod end, as it had very obvious play. Not sure if there's slop in inner tie rod ends. I need a helper to hold steering wheel and/or front right wheel while I manipulate front left wheel and camera records video. Not sure if I see any loosness, maybe a little in left inner, or could be camera angle? |
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dirtkeeper Samba Member
Joined: February 19, 2008 Posts: 3200 Location: Left of everywhere
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Posted: Sun Sep 26, 2021 9:50 am Post subject: Re: Shimmy While Braking After Installing New Wheels |
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Check tire pressure? Tire shops always over fill. Just a thought |
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MrGoodtunes Samba Member
Joined: May 14, 2012 Posts: 852 Location: South Florida
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Posted: Sun Sep 26, 2021 2:05 pm Post subject: Re: Shimmy While Braking After Installing New Wheels |
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dirtkeeper wrote: |
Check tire pressure? Tire shops always over fill. Just a thought |
Thanks for the thought. It was tire pressure that convinced me about what was wrong with the Firestones I had on front wheels a decade ago, because rediculously high pressure would reduce the judder. Normally, I keep front tire pressure in the teens; and my theory is that the sidewalls would sort of buckle or ripple when braking. Back then, the judder was about 1 or 2 pulses per revolution of tire. My current issue is more like 3 or 4 pulses per tire revolution; a more rappid judder, not quite a shimmy. But I haven't yet finish'd going thru the brakes. Fronts all up to par now, gotta find some time to get into rears next. |
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