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Rear end ratios/Brake shoes

jdoclogan

Platinum Level Sponsor
Thought I would start another thread evolving from the Harrington Video thread in the Harrington forum:

I just finished putting together the #41 Sebring Alpine's front axle. I will finish up with the LSD (4.55) rear end tomorrow. We must love putting in the tremendous amount of hours. Whew, and sweat with the occasional blip blip blip.

REPLY: Jumpinjan
On the Tedder Project (Newsletter article back in the day) Ian & I used a 4:22 originally for Mid-Ohio. It was too much. We put a 3:70 gear in it and lap times dropped like many, many seconds.
Jan

I assume that the braking was critical as you carried speed into the corners with the 3:70 gear.
So question: What are the best brake shoes/pads for racing an Alpine?
I literally have several rear ends except the 3:70 which I believe comes from a Hillman.

REPLY:Alpine 64
The first gear in the alpine is so low that the 4.22 makes it barely useful on a street car... And utterly useless on track... A 4.55 would be useful for a hill climb.... I don't think that good on a road circuit.

While Jerry will have overdrive to help with the higher speed sections I'd think the 3.89 would be more useful as a final drive as it will lengthen 2nd gear which is more useful.

Running an alpine on track it's all about carrying speed, i found many corners can be carried in 3rd... A taller 2nd gear would offer more advantage than any acceleration offered by a very short final drive... Just my opinion

Here are some calculations made by Roy Stetina back in the 1960s while he raced his #21 Alpine throughout the mid-west/east coast. My recent acquisition of the Stetina race car came with these calculations. Note: Full page calculations reference Mid-Ohio Elkhart (upper right of document).


upload_2021-1-19_12-49-35.pngupload_2021-1-19_12-50-31.png

The #41 came with a 3:89 installed after its California racing time period 1962-1976. It also had the 4:55 LSD rear end with other parts. From my understanding at this point I would think the 4:55 would be good for hill climbs or autocross. A 3:70 or 3:89 would be best for the track. I also have several 4:22s.
 
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jdoclogan

Platinum Level Sponsor
Thanks Jim. I looked it up and they are expensive. Looks like the shoes are only available in custom form.
 

spmdr

Diamond Level Sponsor
Back last century, Playing with the Tigers, I found Carbotech had WAY better rear brake shoes than Porterfield.

These days, who knows.

I will add, Comparing Tiger Brake NEEDS and Alpine Brake needs, Tigers DON'T have BRAKES if the rears are

not doing their part.

In my limited driving Alpines, the rear brakes are not that critical, in comparison.

Also, when pricing racing rear brake shoe$, be ready for some sticker shock !
 
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jdoclogan

Platinum Level Sponsor
spmdr, I have been shocked!! Any thoughts on the rear end gear ratio?
 
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jdoclogan

Platinum Level Sponsor
DanR, my understanding is: If one wants to stay with originality, which I do, you will be able to run FP class. I suspect that the Sunbeam's drum brakes are adequate for the track by incorporating appropriate brake shoe materials.
 

RootesRooter

Donation Time
I'd think the course dictates which ratio to use. Here in the NW, Pacific Raceways has a very long front straight (also used for drag racing). With 3.89's, my playday runs hit 6,000 long before the end of the straight. 3.70's would have improved my top end. But on a shorter course I'd want the better acceleration from a 3.89, 4.22 or maybe even lower.

BTW, 3.70's were only found on one Rootes/Chrysler UK car in the U.S. The Sunbeam Alpine GT fastback (not the Coupe), and only with automatic transmission. The Sunbeam parts folks in the Netherlands put out repro gears several years ago, but the consensus seemed to be that they are likely to howl from the get-go. I don't know if they even have them in stock anymore.
 

spmdr

Diamond Level Sponsor
Jerry, what max RPM are you planning?

I'm happy with the 3.89 with the limited RPM and small power of the WR Alpine.

When I get the engine to pull 6500+, I will go to a 4.22+.

DW
 

jdoclogan

Platinum Level Sponsor
DW, we look to be on the same page. I've been working to build a 1592 engine to purrr at 4000-6000rpms. Besides the 4:55 Rootes factory LSD described above, I've got a welded 3:89 that is in #21 (Stetina) race car. I may make another welded 3:89 for #41. I have several 4:22 pumpkins and may weld one of those as well. I do have what I know is a Rootes factory LSD in the Promotional Harrington Le Mans. I'm not certain of the ratio. I also have LSD parts from Alcala that appear to be Doanne Spencer's work.

I find, with interest, the 4:86 (I have no idea what vehicle this would come from) referred to in Stetina's chart above to be his star selection. With OD he indicates the final ratio (4th gear) would be 3:90. The chart also shows (with OD) a 4:22 final as 3:39 vs 3:89 final as 3:12.

I have little to no experience on the track and that provides me with minimal intuition as to what might be best. I do like the challenge of processing and even considering any particular track and what would be the best selection. I consider myself holding aces, in my golden years, to have a passion for these kind of challenges. It definitely gets me up every morning to fill my days.
 

RootesRacer

Donation Time
I know its your parts and all but you ought not to weld up those diffs unless you are making your own axles (one piece axles). One common failure the factory had (in racing) was broken axles (broken on the hub taper in the keyway). This makes for a very dangerous set of events that follows the breaking of the axle.
Welded diffs are really hard on axles and there is documented history of failures in predictable places on the axles.
 

RootesRacer

Donation Time
Oh and if you build the right motor, the lowest numerical ratio will be what you want to be competitive on the track. The cars are faster today than they ever were. A 3.70 would be ideal IMO.
 

alpine_64

Donation Time
Jareids warning is very valid, the semi floating rootes rear means when they fail the rear wheel and axle exit the car... A few nasty period photos show this.. An Australian historic racer had a welded diff that caused this failure in the 90s... Very lucky to esacpe serious injury.
 

260Alpine

Silver Level Sponsor
My old International Scout had a tapered axle with a key. I mig welded in about four places on each side of the hub. Stopped the keyway from wallowing out. Basically made them one piece axles. Moser can make custom one piece axles, for a price though!
 

RootesRacer

Donation Time
Yeah, many racing orgs are very wary of two piece axles becuase whenever they are present, there is a higher incident of axle failures. I have been wanting to make me some 1 piece axles for some time, 4 lug ford axles that are wider than ours would make a good donor. The biggest issue is that the alpine rear axle uses a really odd sized bearing OD. So very close to the small 8 inch ford bearing but too small.
 
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