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When I drive my new speedster from Vintage Motor Cars, when shifting up the 3rd the traction is great. When driving in 4rd at 90km/hour ~ 55miles/hours it feels likes that is the max safe speed. Over that speed the car is a bit shaking to the left and right. Is that all normal? Or what are you findings around that?

a beginner with just 800km ~ 500 miles on the car.

Carlos

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Have you had a good shop do a 4 wheel alignment? I’d start there with Danny’s Camber/Caster/Toe In numbers. Also, you may want to play around with tire pressures.



Funny Story: (not really) When I bought my Spyder and drove it home from Chicagoland to NYC, it wandered all over the road. I didn’t do much with it for a few years, then I dropped it off at SE to have some upgrades done.
It wasn’t until I got the car back and swapped out the 165-15’s for 205/60-15 and 195/65-15’s that I realized that the two 4.5” wheels were on one side and the two 5.5’s were on the other.
When I got them properly F/R it handled a LOT better.

And I still have the new ball joints I was going to put on because I thought they must be shot sitting on a shelf.

Last edited by dlearl476

I have the tire pressure test to the advice setting. The car has only 800km ~ 500 miles on it. I ask our mechanic for a 4 wheel alignment. The mechanic noticed that that one of the axle's started to leak, they are fixing that soon, could that have impact on it?

For sure I will ask for a 4 wheel alignment when it goes in for the axle repair.

When I first bought my speedster, I used to travel at a maximum of 65mph on the highways, as that was my comfort level.  The more I drove, the more I got comfortable.    I'm guessing you will as well.  

I recently put 165/15's on my car, switching out the 185/15's. It appears the larger diameter tire (they are slightly over 1" taller) allows the car to travel at higher speeds and lower rpm's.  The new tires are also much more comfortable, but I have traded off cornering ability with the swap.  The steering seems much lighter, as the new tires are 1.25" narrower.  Regardless of the tires I had on my car, I've never experienced any shaking or vibrations.  

With all that said, I'm comfortable traveling at speeds of 80+mph in the car. Someone once asked me if I felt safe doing 70mph.  I told them the way I look at it, I'm dead if I crash at anything over 55mph. (I see these cars as motorcycles with larger fairings)

Your speed is a determination of your comfort level.  Perhaps it's not responsible to go a high rate of speed in these cars (or any older car) as safety wasn't really factored in during the construction of older cars.  Some may say the larger older cars (chevys, lincolns, cadillacs, etc) are safe due to their size.  But I've seen crash test videos that suggest otherwise.

OK, @Carlos P, Here's my 2 cents worth.

I have a full IRS (non-swing arm) car with 205/16" wheels all around.  

All four wheels are original Fuchs (not reproductions) from a 911 (now all 6" wide) and the tires are Michelin something or other running tire pressures of 22 front, 26 rear (yes, they are a tad stiff - I could probably drop a pound or two).

I have had all four wheels/tires "Road Force Balanced" to perfectly dial them in.  It took me almost 20 years to discover this service and get it done and I wonder each time I take her out why it took me so long - It's that good.

I have had a 4-wheel alignment done (1970 VW sedan specs) where the front end caster was set to 6º .  THAT was very important because before that, she wandered, chasing the crest of the lane and any bumps she found.  That made the front end seem squirrely and it wandered a lot, especially with cross-winds.  After a proper alignment and getting the caster between 5º - 7º, she became very stable above 60mph and stays that way all the way up to 100 or so (on the track, of course   ).   It is sometimes still a bit subject to cross winds, but it's a pretty light car so I can live with that and it's minor, to be sure.

I have run a combination of tires of 205/16 front and up to 225 rear (I have a wide body car) and after a proper alignment and caster adjustment I see no highway difference between the larger tires and going down to 205s - It seems to handle similarly on highways with either, but the 225's on the rear REALLY made a positive difference cornering hard on the track.  

So, to summarize;  I feel safe and secure at any reasonable highway speed up to and beyond 85-ish, including riding in the turbulent wake behind a tractor-trailer, given setting my 4-wheel alignment to the 1970 VW sedan specs but adding caster to get to the 5º - 7º range.  THAT made all the difference.

You need more caster than people generally put in their cars. You need something more than a bubble balance on your tires. You need every piece of steering linkage to be "as new" and tightened.

I feel completely fine up to 95. It gets skippy at a buck-ten (not that I'd *ahem* know). At around 100 mph, it's aerodynamics working against you as much as suspension - going faster means setting up the car to be lower. This sets other issues in motion (front caster, and rear camber on an IRS car), but they can be overcome.

If you only feel safe to 55, there's a problem. The car says "speedster" right there on the fenders. It's gotta go faster than a bicycle.

Last edited by Stan Galat

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Stan, Gordon, and others are right about all the suspension and alignment bits that need to be set up right.

But if the car is jumping around at 55, the very first thing I'd check is tire pressure, especially up front. I once had a tire shop set the pressure to 32 psi, because that's sort of normal for sort of normal cars.

But our cars are very light in the front and need substantially lower pressure if you're going to have any grip at all. If they're not already there, set the fronts to 22 psi at most and see if that makes a significant difference.

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Yeah, and with all due respect to your Vintage guys, 26/30 is WAY too hard.  As Mitch mentions, 22 front/26 rear MAX and probably a bit less than that.

On the track, where I would be cornering hard, I was at 24/28 and dropped back down to 20/24 on the street.  That seemed about right.

Oh, and BTW, my CMC has been 4-corner weighed at exactly 2,000 pounds so she's a tad pudgy.

@Carlos P posted:

When I drive my new speedster from Vintage Motor Cars, when shifting up the 3rd the traction is great. When driving in 4rd at 90km/hour ~ 55miles/hours it feels likes that is the max safe speed. Over that speed the car is a bit shaking to the left and right. Is that all normal? Or what are you findings around that?

a beginner with just 800km ~ 500 miles on the car.

Carlos

Carlos,

All of what you need to know is in the archives.

Tire pressure: 22 front, 26 rear. Weight in the front; spare tire & tools or add weight. I have 26 pounds added, no spare. 5-6 degrees of caster (add 2 shims to the front beam). Front sway bar. Rear camber compensator.

Your big engine is worthless if you can't drive the car.

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