[Spridgets] 1275 pressure plate question

Marc smarc at smarc.net
Mon May 11 15:24:09 MDT 2009


Thanks for all the responses. I still think something is not right about 
the clutch kit I put in, so I'm going to pull the lump and install a new 
kit. If you start seeing lots of '73 midget bits appearing for sale in 
the usual places, you can pretty well bet I got sick of screwing around 
with it...



Marc wrote:
> Ok, I have a spare clutch kit I can install if needed. The 'free pedal' 
> concept makes sense to me. I'm guessing that there is some difference in 
> my replacement slave cylinder, with the result effectively being that my 
> push rod is now too long, keeping the TO bearing in contact with the 
> diaphragm and causing an overthrow condition.
>
> In order to obtain the free pedal and appropriate TO bearing clearance, 
> I suppose I'll need to shorten the push rod by some fractional 
> increment(s) until I have it right.
>
> Hopefully, it's as simple as gaining the clearance necessary  and there 
> "should" be ample  travel left for proper disengagement? Um, how far is 
> too far (overthrow condition)?
>
>
> Ron Soave wrote:
>   
>> The instructions on my goofy Tilton clutch are very good in this respect - you
>> put the car in gear, wheels up in the air, verify wheels don't turn. With
>> assistant trying to turn wheels (he's usually curling, but still...) verify
>> pedal is depressed some amount (I forget their exact recommendation, say
>> 5/16") when wheels release. Set stop at some distance past that (like 3/4") to
>> prevent over throw. We set it up with a fancy dial indicator, then just did it
>> by feel at the track when it acted totally different.
>>
>> --- On Wed, 5/6/09, Dave Grandeffo <davegran at tds.net> wrote:
>>
>> Date: Wednesday, May 6, 2009, 3:22 PM
>>
>> David Riker wrote:
>>   
>>     
>>> The TO bearing is supposed to be in constant contact with the pressure
>>>     
>>>       
>> plate.  Like the pads on disc brakes, there is no spring to pull the throw out
>> bearing away.  It is the diaphram spring itself returning to rest that pushes
>> back on the TO bearing....
>>   
>>     
>>> David R.
>>>     
>>>       
>> Not to start an argument, but every clutch I've worked on is supposed to be
>> set up with a measurable amount of "Free Pedal". This means that the first
>> small increment of clutch pedal travel (typically 1/2" -1" or thereabouts -
>> check your manual) doesn't move the pressure plate. In other words, there
>> should be no tension/pressure on the throwout bearing. A lack of free pedal
>> means that the throwout bearing is being held against the pressure plate, is
>> spinning constantly, and will have a greatly reduced life span. This is the
>> same reason you shouldn't come up to a stop sign and stay in gear with the
>> clutch disengaged, no matter what they say in driver's ed....
>>
>> I've never had to replace a throwout bearing on one of my own cars and I
>> usually keep 'em for over 200,000 miles before they succumb to the tin worm. A
>> throwout bearing is not designed to spin constantly.
>>   
>>     
>
>   

-- 

Marc


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