have a vintage flat side speedster and came with 165/80/15 tires on it now, was wondering how tall can you go (trying to lower rpm) was looking at 180/80/15, anybody running these without fender clearance issues ?
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Assume rear swing axle with rear drum brakes and 5.5 x 15" rims?
Do you mean 185/70 x 15? There doesn't seem to be a 180/80 15 on Tirerack.
Suspect there is little difference in diameter.
Wolfgang, yes exact setup I have, sorry not posting that info, if theres not much height difference guess I'll keep what came on it, was wondering what the tallest one I could get under the rear without fitment issues.
I'd look at 16 or 17 wheels - can always get new drilled drums or rotors. Try Miata tire size calculator -
Specification Sidewall Radius Diameter Circumference Revs/Mile Difference 165/80-15 5.2in 12.7in 25.4in 79.8in 794 0.0% 185/70-15 5.1in 12.6in 25.2in 79.2in 800 -0.8%
Practically speaking the 165-80/15s are your car's tire size. You might find some bigger ones but much bigger you're going to have fitment issues, and well as style issues.
If your revs are too high on the highway, the fix is the gears in the box. What's your RPM at 70 mph?
Instead of raising your car and making it look stupid, your best bet would be to get a taller final drive in your transmission. The factory VW is either a 4.12 or a 4.37. Taller would be 3.88 or 3.44.
Honestly, though, these engines are REALLY happy around 3000 rpm. I wouldn't suggest cruising at less than 2500 rpm. What rpm do you cruise at? Or want to?
cip1.com has a 3.88 R & P for $550 right now.
Don't know as I will be driving it tomorrow on the highway as it was just registered, has the 3.88 setup in it, was just trying to keep it low as its 1/2 of highway to beach house, will let you know where the tach is @ 65-70ish tomorrow.
With a 165/80R15 and a .89 fourth with a 3.88 R/P, 3500 RPM is 76.6 mph. If you want to drive 85 mph, you'll need a 3.44 - tires won't do it. 85 mph with your setup is 3900 RPM. You won't like it.
@DannyP posted:Instead of raising your car and making it look stupid, your best bet would be to get a taller final drive in your transmission. The factory VW is either a 4.12 or a 4.37. Taller would be 3.88 or 3.44.
Honestly, though, these engines are REALLY happy around 3000 rpm. I wouldn't suggest cruising at less than 2500 rpm. What rpm do you cruise at? Or want to?
cip1.com has a 3.88 R & P for $550 right now.
Listen to Ed, Danny and Stan- you won't be able to fit anything tall enough to make that much of a difference, and really tall on the back of a Speedster does look kind of gorkey (I know, the boys already said that, but they didn't use the technical term). Actually, the 3.88 is a VW factory r&p as well- it is found in later type 1 transaxles (after about mid 1973?). It's just not as common as the 4.37 and 4.12. And as Danny said, cruising at less than 2500 rpm in 4th (especially with a stock stroke engine) can result in overheating- the fan won't be turning fast enough (and pushing enough air) to cool the engine when going up any incline steep enough that the engine is into the main (power) circuits of the carbs.
The shift points on a stock speedometer are 15, 30 and 45 mph- it's not smart to run the engine with a load on it in the upper gear below the shift point. I bought my first Beetle in 1974 (my first car- I was 17) and anyone experienced with VW's would caution you against "lugging it"- it was (and still is) a quick way to destroy an engine. If the rpm's were so low the car wouldn't accelerate, it was time to downshift.
@widebody boy posted:Don't know as I will be driving it tomorrow on the highway as it was just registered, has the 3.88 setup in it, was just trying to keep it low as its 1/2 of highway to beach house, will let you know where the tach is @ 65-70ish tomorrow.
What engine are you running, and how high (as ALB asks, always) does it rev with power? The answer to that will determine what gear ratios and tire heights will work best.
My bet is you don't have a problem. To be sure, I suggest you double-check your speed with a stand alone GPS, and also make sure the tach is close to right at 3000 RPM. Also warm it up, find a straight road, put it in second and blast it til it starts to fall off. Let us know what RPM that was.
My 2010 Corolla does about 2900 RPM at 70 mph. Let's call that the normal(ish) modern car highway tach speed.
A 4.12 R&P and .93 4th gear will turn about 3000 RPM at 60 mph with those tires.
The 3.88 with the .93 at 3000 RPM is about 63 mph
The 3.88 with the Ghia .89 4th gear at 3000 gives almost 66 mph
All of these are fine, btw, with the cammed-up engines we run. Our cars sound loud and cranky because they're old tech, but 4000 rpm on the highway is not going to harm them at all. In most cases, 4000 is right about peak torque. That's the engine's happy place. A stock 1600 would be revving high at 4000; a CB Performance 2110 is just getting ready to sing the song of its people.
But we're so used to silent cruising with V8 power, hearing our Speedsters and Spyders trips the worry circuit in our brains. A Ford F150 running 4000 rpm on the highway would be a problem: shift!
To achieve modern car cruising RPMs, install a 3.44 ring and pinion.
The 3.44 with the stock .93 4th at 3000 RPM gives 71 mph. That's Corolla-equivalent. That's what I have in my Spyder, and my Subaru-powered MG. Works for me!
The 3.44 with the .89 4th at 3000 RPM is 74 mph. I believe that is the outer limit for an air cooled engine in a Speedster, and more than many would want to pull. As ALB notes, your engine wants to rev, because revs=fan speed, and fan speed=cooling.
Understanding that, be aware of a trick that got popular a couple decades ago but is generally not recommended: the .82 4th gear.
That gear can work! But if it's the only one you change, it creates too much of a 3-4 gap. A box with an .82 4th also should have taller 1st, 2nd and 3rd gears.
Now...the 3.44 R&P would appear to be the panacea. Install it and cruise like a modern car! And, indeed, it's a very good compromise, as it also pulls the VW Beetle's stock 3.80 stump-puller 1st gear into the realm of something useable. But! Every little decrease in gear ratio saps a little bit of the "snappiness" from the drivetrain. If you like to jam the car through the gears between stoplights, and yearn for that pushed-back-in-the-seat experience, the 3.44 is not the way.
This concludes my Ted Talk.
Ed's post seemed Gordon-long, but was actually as concise as possible to convey the lay of the land. It's also why all the cool kids run 5-speeds. I wish I were cool, but I'm not.
Where I depart from the orthodoxy is in what an appropriate RPM range for cruising is. A big T1 (2110 and up) doesn't want to be operated at 4000 RPM continuously. Yes, it's right at the torque peak, but the engine is not happy to do it for 8 hrs straight across the high plains in July or the desert in the afternoon. My maximum acceptable RPM for continuous cruise is about 3800 RPM, and my sweet-spot is 3000- 3500. More than 3800 and you'll start to lose control of your temperatures -- both head and oil.
There have been guys on this forum who have claimed that they've got a 4-speed that is "just as good" as a 5-speed. It may be just as good for their use, but it cannot ever be everything all the time. I've had multiple transaxles with every imaginable 4-speed combination looking for the holy grail. For "all around" use, assuming a "normal" amount of interstate highway use - a stock 1st and 2nd (called a main-shaft), a 1.3 third, a .93 fourth, and a 3.44 R/P is as good as it gets. If you're not going to be on the highway that much the same ratios with a 3.88 R/P will move you more briskly.
It seems like a more powerful engine would take care of the problem, but you can't build a big enough engine to fill in the low spots that the missing gears would take care of. Subarus come close, but even a Subaru comes from the factory with a 5-speed.
Forewarned is forearmed.
Rejoinder:
The 3.44 and .93 in my cars at 4000 RPM gives 94 mph.
The 3.88 would be 84 mph. The 4.12 would be 79 mph.
Like I said: you probably do not have a problem that needs solving.
ALB is right on that Ghia/Thing/and later '73 T1 bugs used 3.88 R&P. Some had LSD (but probably none exported to the US). I found a chart years ago that listed codes and internal gears but the link is gone now. Here's one that has some info. Unlike VW engines, many trans have been untouched internally. Some are swing axle vs IRS, some take different diameters (180-200 mm) flywheels (and throwout bearings), and the nose cone is different in later ones.
My Vintage Speedster came with Pirelli P4 185/15's (24.40" diameter). In 2021, I swapped them out for Vredestein Sprint Classic 165HR15 (25.40" diameter). For my driving style, I couldn't be happier. The sprint classics are 1" taller. The sidewall is thicker. They are more narrow than the Pirellis, but in terms of comfort, I'm happy I got them.
Highways speeds are at lower rpms since swapping out the tires. I believe 85-88mph is around 4,000rpm's with my freeway flyer gear ratios. I tend to cruise at 3500--3600RPM's, which is fast enough to scoot around modern traffic.
went for my first ride on the highway today, you guys were right, keeping up with traffic @ 3000 rpms no problem, couldn't really tell ya how fast I was going as speedo was saying 100mph ?? don't know how that could be geared wrong but, last one I owned had gps speedo, any ideas on the speedo let me know, Thanks
FWIW, I went for a more aggressive look/stance with my swing-axle VS. Wider and lower tires 185x60x15 on 5.5" wheels with 4" offset. 1915cc engine, 3.88 gear (fwy flyer?), external oil cooler & filter.
At 3,000rpm in 4th I'm doing 73mph. I frequently run at this rpm & speed during the 5-hour drive to our favorite getaway on the California Central Coast. Never had cooling issues.
Click on picture to enlarge...
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@widebody boy posted:went for my first ride on the highway today, you guys were right, keeping up with traffic @ 3000 rpms no problem, couldn't really tell ya how fast I was going as speedo was saying 100mph ?? don't know how that could be geared wrong but, last one I owned had gps speedo, any ideas on the speedo let me know, Thanks
100 kph is 62 mph which is suspiciously what you will get at 3000 rpm's in a stock geared transmission. Just saying.
@edsnova posted:the 3.44 is not the way, unless you have the motor to push it.
This concludes my Ted Talk.
I agree with Ed, except this last point, which I've edited.
@MusbJim posted:Never had cooling issues.
Jim doesn't overheat. Jim doesn't measure his head temps. Jim's heads would not deign to fuss.
Because Jim subscribes to the KISG attitude, which stands for Keep It Simple Guamaniac. I wish I was as carefree, but hey, it works for him!
@WOLFGANG posted:ALB is right on that Ghia/Thing/and later '73 T1 bugs used 3.88 R&P. Some had LSD (but probably none exported to the US). I found a chart years ago that listed codes and internal gears but the link is gone now. Here's one that has some info. Unlike VW engines, many trans have been untouched internally. Some are swing axle vs IRS, some take different diameters (180-200 mm) flywheels (and throwout bearings), and the nose cone is different in later ones.
From what I've seen in the REAL world:
A trans case with 2 side covers and 2 drain plugs is LIKELY to be a 4.37 R&P.
A trans case with 2 side covers and 1 drain plug is LIKELY to be a 4.12 R&P.
A trans case with a SSC(single side cover) is LIKELY to be a 3.88 R&P.
The first 2 transmissions COULD be swing axle OR IRS. The last MUST be an IRS trans.
Now, anything COULD be inside if they've been opened up or rebuilt before.
@widebody boy - Darrell wrote: "went for my first ride on the highway today, you guys were right, keeping up with traffic @ 3000 rpms no problem, couldn't really tell ya how fast I was going as speedo was saying 100mph ?? don't know how that could be geared wrong but, last one I owned had gps speedo, any ideas on the speedo let me know, Thanks"
Ain't nothing wrong with your tranny OR your Speedometer!
Keeping up with traffic on RT 24 or someplace like that will be 65mph or so, which if you have a speedometer reading in Kilometers, would be around 100kph!
Sounds like you've got a Kilometers Speedo. If you look on the face at the bottom, it should look like this: Kilometers/hour
Take whatever it is reading, multiply by 6 and drop the last digit, so 100 x .62 = 62 , 120 x .62 = 74, 130 = 80 and so forth. If I'm right, you'll get good at reading your speed in a couple of drives (Using Waze on your phone helps). You also get to know where 35 (55kph) and 45mph (75kph) are by the angle of the needle. I find it's easier to just multiply by 6 in my head and guestimate the rest.
I may be wrong about all of this, but I bet I'm not.
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Gordon you are right, just gave it a bath and wax job , looked at speedo and it was kph, I believe it has the 3 88 setup as there is a huge gap from 3-4, nice on the highway.
@widebody boy posted:Gordon you are right, just gave it a bath and wax job , looked at speedo and it was kph, I believe it has the 3 88 setup as there is a huge gap from 3-4, nice on the highway.
If there is a HUGE gap from 3-4, then you probably have 4.12 R&P, stock 1-2-3, and .82 4th gear.
The 3.88 R&P with stock 1-4(3.80, 2.06, 1.26, and 0.89) drives very nicely, and 3-4 shift doesn't feel HUGE. It feels just about RIGHT.
There are online calculators, and there are even guys who have done spreadsheets where you jack one rear wheel up and turn it X times to get Y times engine rotations equals Z gearing.
OR, you take it apart and count teeth.
OR, you can pull the drain plug and count ring gear teeth with a light and a mirror and mark one. 35 is a 4.37, 33 is a 4.12, and 31 is a 3.88. All the pinion gears have 8 teeth.
That is, except the 3.44. That one is 9 with 31 on the ring.
Fun fact: there are odd-numbers of teeth on the ring so that the same teeth do not constantly mesh with every revolution as they would if the numbers were evenly divisible with no fraction. Neat.
@edsnova posted:The 3.88 with the .93 at 3000 RPM is about 63 mph
The 3.88 with the Ghia .89 4th gear at 3000 gives almost 66 mph
If the gap from 3rd to 4th seems a little wide you probably have the .89 4th gear and your speedo reads a shade low. This would also tend to be the case if 100 kph on the speedometer found you passing modern highway traffic.
Anyway: good on ya. No changes needed!
Wow! I got one right!
Gonna have a Treehouse Stout to celebrate!
@Gordon Nichols posted:Wow! I got one right!
Gonna have a Treehouse Stout to celebrate!
Gordon, look 2 posts above your post. I had it nailed. 
