front end bumping
Thread Starter
Instructor
Joined: Jan 2014
Posts: 178
Likes: 43
From: Massachusetts
front end bumping
I have a 1964 C2 convertible with the 327/365 engine. L76. No power steering, no power (drum) brakes, no A/C, basically the base 1964 convertible with the 365 hp engine as the only option. It is the 4 speed manual. I have only had this car for about 6 weeks and I really enjoy it.
When I drive the car and shift through the gears, 1st gear is fine, 2nd gear is fine, but when I get to 3rd and 4th gears between 3000 and 3500 rpm, the front end bumps like the tires are out of balance. I just replaced all four tires which were very old. I assumed that the old tires were out of balance or had flat spots but this is happening with the new tires. The clutch and transmission seem OK. The shop that mounted and balanced the tires is a excellent Corvette repair shop. I asked the owner what he thought about the transmission and he said it seems fine. I want to get this fixed but I want some ideas what may be causing this before I go back to the Corvette shop.
Any ideas what may be causing this?
When I drive the car and shift through the gears, 1st gear is fine, 2nd gear is fine, but when I get to 3rd and 4th gears between 3000 and 3500 rpm, the front end bumps like the tires are out of balance. I just replaced all four tires which were very old. I assumed that the old tires were out of balance or had flat spots but this is happening with the new tires. The clutch and transmission seem OK. The shop that mounted and balanced the tires is a excellent Corvette repair shop. I asked the owner what he thought about the transmission and he said it seems fine. I want to get this fixed but I want some ideas what may be causing this before I go back to the Corvette shop.
Any ideas what may be causing this?
Race Director
Joined: Jan 2002
Posts: 15,354
Likes: 2,726
From: Close to DC
C2 of the Year Finalist - Modified 2020
What speed are you registering in the 3-4th gear range? Are you feeling this bumping through the steering wheel, the seats, or is the front body shaking? I'm guessing you have a suspension problem. What do you know about the shocks? 
Dennis
Dennis
Race Director
Joined: Jan 2003
Posts: 17,696
Likes: 3,683
From: Central Arkansas
If the shocks look really old they may be shot. Back in the late 60s I bought a used car that the tires dribbled or bounced at higher speed. I didn’t know the cause at the time but put a new set of shocks on it and it went away. Also, did the tire shop check the alignment?
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Instructor
Joined: Jan 2014
Posts: 178
Likes: 43
From: Massachusetts
I drove the C2 today and got it up to 50-55 mph and 3000-3500 rpm and took it out of gear and the bumping was still there.
As for the tires, the old set of tires did this same thing as the new tires are doing so I tend to feel that the issue is not in the tires but as Bluestripe67, DansYellow 66, and SJW said, it sounds like an issue with the shocks and suspension.
Would you recommend a newer shock such as a Bilstein or go with replacement replicas like came with the C2 originally?
Thank you all for your help.
As for the tires, the old set of tires did this same thing as the new tires are doing so I tend to feel that the issue is not in the tires but as Bluestripe67, DansYellow 66, and SJW said, it sounds like an issue with the shocks and suspension.
Would you recommend a newer shock such as a Bilstein or go with replacement replicas like came with the C2 originally?
Thank you all for your help.
Le Mans Master
Joined: May 2005
Posts: 7,362
Likes: 2,282
From: Central Maryland
I would check all steering and suspension components for wear and damage. Although you reported that there was no change when new tires were installed, it would be wise to check for runout at the wheels & tires. As Dan noted, new shocks might solve the problem - is there evidence of leakage of the existing shocks? Is a steering damper present on the car?
Live well,
SJW
Live well,
SJW
Pro
Joined: Jun 2007
Posts: 547
Likes: 264
From: Quebec, Canada
You've obviously got something that's wiggling. You don't really notice it when it's below its resonance frequency. But when you get to 50 m.p.h. it resonates and self-amplifies, so that's when you notice it. It's the same principle as the Tacoma bridge collapse in 1940. Shocks are there as a damper to stop the suspension from bouncing up and down, not to correct something that's loose or out of balance and wiggles. If you know for sure that your tires are balanced and not out of round and the wheels are straight, you need to check that there's no play in the suspension or steering. I'd start with the wheel bearings and tie-rod ends. If I had to place a bet, it would be tie-rod ends.
Last edited by scowser; May 1, 2025 at 10:13 PM. Reason: punctuation
Race Director
Joined: Jan 2003
Posts: 17,696
Likes: 3,683
From: Central Arkansas
There are 2 different types of Bilstein shocks available and I believe the HD series would be what you want as the Sport series is pretty stiff. But any quality gas shock would probably work fine. What about the alignment question - has it been checked? It could be a combination of things coming together like near zero caster, weak shocks, some looseness in ball joints or tie rods, etc.
Team Owner
Joined: Apr 2008
Posts: 31,807
Likes: 2,399
From: Middle TN by way of KY, OH, VA, IL, CA, FL, NY, SC, HI
I would have a professional go through your front end/suspension checking every ball joint, shock, tie rod end, idler arm, wheel bearing, sway bar link and bushing, steering box, control arm bushing, etc., for wear, excessive play, and tightness. I had a ball joint come apart on a car (not a Corvette) about 40 years ago and was lucky it didn't do so at speed. Did the old tires show any cupping or other odd wear patterns?
Team Owner
Joined: Apr 2008
Posts: 31,807
Likes: 2,399
From: Middle TN by way of KY, OH, VA, IL, CA, FL, NY, SC, HI
Thread Starter
Instructor
Joined: Jan 2014
Posts: 178
Likes: 43
From: Massachusetts
I'm going to have a garage thoroughly check out the front suspension, etc. They do a lot of work on older Corvettes.
What I meant when I said there is "bumping" at certain speeds is what you feel when you drive over real small speed bumps and it is noticable in the front only and seems to be more pronounced on the front driver's side.
What I meant when I said there is "bumping" at certain speeds is what you feel when you drive over real small speed bumps and it is noticable in the front only and seems to be more pronounced on the front driver's side.
Race Director
Joined: Jul 2018
Posts: 10,595
Likes: 8,418
From: San Antonio, TX/Mahopac, NY
2026 Restomod of the Year Winner
2024 Corvette of the Year Finalist - Modified
2024 Corvette of the Year Finalist - Unmodified
2023 C7 of the Year Winner - Modified
I’m guessing either wheel bearings, tie rod ends, or control arm bushings. It’s only a guess because without proper diagnostic work we are all guessing and these are the other things that can cause vibration in the front end. OP, please post the results of what the shop finds.
Team Owner
Joined: Sep 2002
Posts: 38,361
Likes: 2,085
From: California
Too much could be wrong, just to add to the list of things mentioned to look at, also check the attachment of the lower a-arms as welding there could be an issue! I assume the rims were checked, when the tires were changed! Does the car wander?