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Longer Gearing


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#1 happydude2012

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Posted 09 November 2017 - 11:01 AM

My 1275 A series is currently 4 speed.

 

On a previous rolling road test, the engineer said due to the sw5 cam, the car felt "under geared" and would do well with either a 5th gear or a wider ratio for 3rd and 4th.

 

Ive looked at 5 speed boxes and they are £2000+, does anyone have any experience with this issue?

 

 



#2 Steve220

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Posted 09 November 2017 - 11:09 AM

5 speeds dont take high power well. If you like the 4 speed, then change the final drive in your current box.

#3 Jarvey

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Posted 09 November 2017 - 11:20 AM

As above really, the final drive / gearing will change things massively but if you go for a long legged final drive ( such as 2.76 from an MPI ) you lose out on acceleration but can cruise @ 90 all day.

 

Also 5 speed boxes, apart from a racing dog box are over-driven 5th gears which in my mind wont be very strong and is kind of a work around instead of having 5th being part of the main shaft. But like you say they ain't cheap either way! 

 

 

Ah ... compromise, gotta love Mini tuning haha.



#4 DomCr250

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Posted 09 November 2017 - 11:30 AM

I had a 2.9 diff and 13" wheels, to be honest it did not really impact the acceleration that much and made for relaxed driving.

 

Have a play with this http://www.crawlpedi..._calculator.htm - 4th gear is a 1:1 ratio on a mini and use this http://www.tyresizec...tire-dimensions to work out your tyre size in inches.



#5 nicklouse

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Posted 09 November 2017 - 11:33 AM

My 1275 A series is currently 4 speed.

 

On a previous rolling road test, the engineer said due to the sw5 cam, the car felt "under geared" and would do well with either a 5th gear or a wider ratio for 3rd and 4th.

 

Ive looked at 5 speed boxes and they are £2000+, does anyone have any experience with this issue?

 

 

so what gear set is in the gear box? what is your current final drive.

 

find/work these out then real advise can be given.



#6 Northernpower

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Posted 09 November 2017 - 11:34 AM

My 1275 A series is currently 4 speed.

 

On a previous rolling road test, the engineer said due to the sw5 cam, the car felt "under geared" and would do well with either a 5th gear or a wider ratio for 3rd and 4th.

 

Ive looked at 5 speed boxes and they are £2000+, does anyone have any experience with this issue?

 

 

I'm surprised the rolling road said the car was under geared. With the correct spec the SW5 will rev over 6,500. What's the spec of the engine and what's the current FD?



#7 Moke Spider

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Posted 09 November 2017 - 04:41 PM

The Mini Spares 5 Speed are no weaker than a stock box.



#8 Ethel

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Posted 09 November 2017 - 05:28 PM

This one has all the Mini ratios typed in for you to experiment with:

http://www.guess-wor.../Tech/ratio.htm

 

The SW5 is a road cam so it shouldn't be any worse than before.  You need to consider how you're going to use it, will fuel economy and bleeding ears be a consideration...?



#9 happydude2012

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Posted 09 November 2017 - 07:12 PM

Ill be honest - i absolutely crap myself over 60-70 mph because of the high revs, i know its normal on a mini but that high rev noise in the back of my mind makes me think the engine is about to explode. I probably dont give the A series enough credit, its a good strong motor in this car, i just wish i could motorway drive without that fear of exploding it.



#10 happydude2012

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Posted 09 November 2017 - 07:16 PM

i should also say, im not after massive speeds, ive grown out of that and reliable but fun is what im after. I dont know my gear ratios now and as a car i need daily, i dont have the time or expertise to strip it all down and look. (I wouldnt know what i was looking at anyway. ha ha)

i think id just like a nice set of straight cut - i can handle the noise as my dads minis always had straight cut.....(pulls over at services... "DAD!"...."What?"...... DAD!!...."eh??"   DAD!!........"Did you say something Son?"........" You what?"........"huh?"  . etc etc)



#11 happydude2012

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Posted 09 November 2017 - 07:17 PM

i should also say, im not after massive speeds, ive grown out of that and reliable but fun is what im after. I dont know my gear ratios now and as a car i need daily, i dont have the time or expertise to strip it all down and look. (I wouldnt know what i was looking at anyway. ha ha)

i think id just like a nice set of straight cut - i can handle the noise as my dads minis always had straight cut.....(pulls over at services... "DAD!"...."What?"...... DAD!!...."eh??"   DAD!!........"Did you say something Son?"........" You what?"........"huh?"  . etc etc)

not to mention hitting something in a tin can @ 100mph, is not my idea of fun



#12 Minigman

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Posted 09 November 2017 - 07:32 PM

I recall going to Slarks rolling road a long time ago and they revved my well built 1275 to 7000rpm. I trusted them completely they know what theyre doing after all. However the sound of that engine revving its nuts off changed me forever and Ive never revved a mini beyond 5,500 since. I literally cant bring myself to do it. Haha. Ive never used a hotter cam than a 266 since.

#13 nicklouse

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Posted 09 November 2017 - 09:48 PM

 

i should also say, im not after massive speeds, ive grown out of that and reliable but fun is what im after. I dont know my gear ratios now and as a car i need daily, i dont have the time or expertise to strip it all down and look. (I wouldnt know what i was looking at anyway. ha ha)

i think id just like a nice set of straight cut - i can handle the noise as my dads minis always had straight cut.....(pulls over at services... "DAD!"...."What?"...... DAD!!...."eh??"   DAD!!........"Did you say something Son?"........" You what?"........"huh?"  . etc etc)

not to mention hitting something in a tin can @ 100mph, is not my idea of fun

 

define high revs?



#14 timmy850

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Posted 09 November 2017 - 10:23 PM

Mine does 4200rpm on the highway for hours. It's only about 60mph with my short diff ratio (3.76) but the engine is designed to do those kind of rpm. 



#15 Cooperman

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Posted 09 November 2017 - 10:47 PM

A 3.44:1 FDR will give c.16.5 mph/1000 rpm in top. Thus at 60 mph the engine will be running at 3600 rpm which is relatively low for an old A-series engine. Cruising at 70 mph will give 4250 rpm which is still not excessive.

 

Remember, we are talking about old classic cars here, not modern fuel-injected units.

 

I am happy to rev an A-series to 6000 rpm, even a 1098 unit and a good 1275 should be OK at up to 6500 rpm.

 

You don't buy a classic car for smooth relaxed low-revving cruising. You buy one for the retro-driving experience and the fun.






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