• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

TR6 TR6 Top Speed?

Share this page

C

crj7driver

Jedi Trainee
Offline
Does anyone know how fast the race preprepared TR6's were? In my turkey induced coma I was contemplating how fast a 6 can <u>safely</u> go.

I did some calculations and my little bastardization project should yield a car that should do 165-175 mph. Gearing wise it will do 195, but the drag on the oh so aerodynamic 6 stops it around the 170 mark.

I was just curious how fast you could safely drive on a track or desolate Wyoming road. From what I understand you are pretty safe until 150 mph then aerodynamics start playing a major factor. Before the tear down I had it up to around 100 indicated on the stock motor and it felt light but stable.

Just curious what your high speed impressions of the 6 were on the road or track. BTW, the is mainly an academic question as I have a motorcycle that will do just shy of 180mph, but it has never seen even close to that, but it is nice to know that it is stable at the top end.

Thanks, now back to the honey-do's before I am free to the garage.
 
Don't have any idea what the theroretical top speed is.
I know when I've had mine over 100 mph there's still quite a bit of pedal under my foot
I've got to admit that's about when I get nervous thinking about all the bolts and components in the running gear and what would happen if they came apart at that speed
 
I've had mine at a non publishable speed and my only concern was the old suspension and hydraulic brake system, which is now being replaced completely.

I've also had mine at 110MPH on the dyno in 4th gear at 5,400 RPM's. I had plenty of pedal left on the highway in OD, but not enough guts to see where it may lead on those old parts.
 
170 mph is awfully fast! My estimate is that you would need something over 300 hp at the flywheel to push a TR6 that fast. You must have some pretty wild engine work going on!

Be careful (but have fun)!

Bryan
 
My stock '73 did about 125 floored, and with a tailwind, pushed 130. At those speeds it began to overheat...

That was in 1980. Would not do it now.
 
I know I'd never be in a TR6 at 170MPH.

Not unless it was on a 1/4 mile track, it had a parachute and was on a different chassis and brake system.
 
Took the Mrs up to 135 mph on the back of my tricked
out crotch rocket on Rt 95 in Maryland. (informed her
AFTER the event took place!). I never quite had the
cajones to take it over the 150 mph mark.

I've had Amos at only a little over 80 mph.

d
 
My '64 TR4 could make 115 to 120 on the flat and my '67 GT6 could do 140 with some downhill with ease. Both handled well at those speeds. The GT6 was absolutely beautiful at that speed. Even impressed State Patrol witnesses. /bcforum/images/%%GRAEMLIN_URL%%/crazy.gif No sense of humor, those guys! (seems they did not have time to both read the radar and identify the car)

However those cars were new and the suspensions and brakes were also new and in perfect condition.

With out overdrive, my TR6 is quick to hit 100 uphill, downhill, or on a flat, with plenty left and a considerable feel of acceleration when the pedal is pushed down. However it is not something I have done more than a couple times and do not consider it real smart like it seemed years ago. And this car and its suspension and brakes are 30+ years old. Seems like it is a disaster waiting to happen.

With the increased population, bicyclists, pedestrians, and country homes with children, say nothing of the heavy traffic and increased police and their radios is really seems like a murder/suicide wish or an application for the looney bin.
 
Some of the guys running the FAST TR6's at TRF Summer party drag races over the years had problems with keeping the front end firm to the ground at high speeds. I don't know what speeds they were doing, but a fellow running nitrous wanted to remove his hood to eliminate the problem.
 
DougF said:
Some of the guys running the FAST TR6's at TRF Summer party drag races over the years had problems with keeping the front end firm to the ground at high speeds. I don't know what speeds they were doing, but a fellow running nitrous wanted to remove his hood to eliminate the problem.
Click to expand...


Thanks, that is what I thought when driving the car. I think it is pretty stable up to 125-130 after that you would need some aerodynamic aids to make sure things stay planted. I think when the speedo pegs it is time to let of on the happy pedal as it is probably what the factory designed it for.

Now I just need to finish it and take it to the track to see how it goes (so I don't have to fear being arrested).
 
I know that it depends on the diff that you have installed, but I thought that the general rule of thumb for a non-OD TR 4 to 6 was:

3000 RPM = 60 MPH
4000 RPM = 80 MPH
5000 RPM = 100 MPH etc. etc. Brosky's dyno numbers seem to support that for the TR6.

There must be some well balanced stock engines out there to do a sustained run past the red line in order to gain the higher RPMs needed for those speeds. Also are they on original sized tires or modern lower profile ones? My TR4 speedometer reads high by about 5% when checked against my GPS, due to the modern tire profile.
 
I've read a couple of old road tests that put the top speed of a TR6 at about 109-115mph. Which based on the horsepower and the ever stylish "brick in the wind" aerodynamic shape, sounds about right. Not saying that the above posts didn't see speeds that they reported, but usually speedometers are calibrated to be most accurate between 50-60mph; after that the faster they go the more inaccurate they become.
 
I've had it to the (indicated) ton before my courage gave out. Based on driving other - newer and faster - cars on the same stretch of road, it was closer to 90 than to 100. Felt like 150 though!

That was before the engine mods and suspension rebuild. It was wandering across 2 lanes and I was about as scared as I'd been in anything, ever.

I too would be curious to know how fast it will go. I know the PIs at 150hp were good for about 120. With an all out racer now pushing 250hp on triple Webers, they ought to be good for a little more than that.

I guess we should ask TRED. I'll bet his TR6 will do 170 easily. Probably in 2nd gear /bcforum/images/%%GRAEMLIN_URL%%/wink.gif
 
Shannon,

One of the things that I was curious about with the dyno runs was the accuracy of my gauges, for two reasons.

1. I wanted to know if they were correct at high speeds as you said.

2. I didn't want to wait five or six weeks to have them calibrated and rebuilt when I took the dash apart this winter/spring.

In the frame below, my tach was right on the money with the tach on the dyno.

My speedo was reading about 2mph faster than this at 104MPH.

So all in all, I'm satisfied that if I were stupid enough to get it up to 125 on the highway, that it would be safe to assume that I was traveling at 120MPH.

Again, safe to assume, stupid to actually do.

John of NE Dyno told me that he felt they were as good as could be expected for 34 years old and 54,000 miles of travel.
 
Paul,

Wow, that's close.. especially considering new vs. old tire sizes. I know the last car that I had dyno'd (Supercharged 2000 Mustang GT) was about 5mph off at top speed in 4th gear. I've heard speedo's being as much as 15mph off at over 100mph.

After a little more research, I've found several road tests that pegged the 150bhp PI model at 119mph and the US model at 109mph.

A top speed calculator that I found says that at 5500rpm using 185/80-15 tires with a 1:1 4th gear and 3.70 final drive would render 117mph. I believe that the European cars had a 3.40 final drive which puts top speed at 128mph. Of course these numbers are theoretical and don't take into account the engines ability to actually propel the car to those speeds.

Interesting that, based on the road test numbers, neither car was able to hit 5500rpm in 4th gear.
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:] Interesting that, based on the road test numbers, neither car was able to hit 5500rpm in 4th gear.[/QUOTE]

Shannon,

Due to a lack of sufficient testosterone, neither was I on the highway.
 
Back
Top