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Gtir Motorsport club » General Discusion » Random banter » took evo for mot .. have concerns about brake tester

took evo for mot .. have concerns about brake tester

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ROB_IOW

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the two star club
the two star club
Evo flew through its mot today .. should hope so coz it's only done 630 miles since last year .. Now in the past its always been driven on the road for its brake test .
This year they have a new brake testing machine  2 rollers only . .

Now he tested the evo on this brake tester
Should I be concerned ?
He said coz it's a 4x4 They spin The wheels in opposite directions .
But obviously the wheels that ain't in the rollers don't spin

I'm sure my evo has a slippy diff in the back . Surely this won't have done the diff any good or the centre diff ..

Mr B

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gtir technician
gtir technician
On a open diff it would be ok as when wheels rotate in opposite directions at equal revolution then prop would not rotate & open diff itself would function fine.
Yours is mechanical plated diff and perhaps AYC as was factory option on GSR 4's
I would road test them only for LSD diffs ...

kevmc76

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I think you are correct rob

ROB_IOW

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the two star club
the two star club
Should I be concerned?

Mr B

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gtir technician
gtir technician
I wouldn't let them do it again ...

Gostek

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Events Organiser
Events Organiser
You can't test permanent awd car on normal roller (one axle tested at the time) because you're risking damaging centre diff. You can't test rwd car with lsd either (not even on automated test line) because you can't start rollers at the same time this is what they told me at mot course... Don't know what sort of brake rollers they've got bud but I personally wouldn't put awd car on brake rollers.


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Gostek

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Events Organiser
Events Organiser
@Mr B wrote:On a open diff it would be ok as when wheels rotate in opposite directions at equal revolution then prop would not rotate & open diff itself would function fine.
...
At one point you need to spin both wheels together so I'd say even open diff wouldn't be ok


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Mr B

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gtir technician
gtir technician
^ In that scenario then no, I assuming they only do a basic test of brake function while spinning opposite directions rather than a full test & balance comparison.
Only way I can see it being fully safe on awd is portable floor roller plates to put under axle wheels not in test rollers .

ROB_IOW

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the two star club
the two star club
Could a pulsar be tested in this manner ?

johnny gtir

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moderator
moderator
Would say no as don't you need all 4 wheels independent so how would you get the potable roller under the wheel where the mot roller is or am I picking this up wrong ?

Gostek

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Events Organiser
Events Organiser
From what I've heard you can test on 2wd rollers stuff with haldex system I've tried once on 07 audi tt and it jumped out of the roller so I do any permanent 4wd cars now only with decelerometer. Oh on this note how did he managed to keep car in rollers?? Surely it wanted to drive out...


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ROB_IOW

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the two star club
the two star club
One wheel was spinning forward and one was spinning backwards on the rollers
Somthing about spinning then opposite ways cancels out the prop

Gostek

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Events Organiser
Events Organiser
@ROB_IOW wrote:One wheel was spinning forward and one was spinning backwards on the rollers  
Somthing about spinning then opposite ways cancels out the prop

To be honest I'd need to see how this setup works but to check brake imbalance you need to spin both wheels forward at the same time. Still I personally wouldn't risk it especially knowing (or even suspecting) that car got lsd too. I'll ask my other tester mates if they've heard about set up like that but somehow I don't think so... Have you actually seen it being tested??


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ROB_IOW

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the two star club
the two star club
I was stood next to it ..

ROB_IOW

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the two star club
the two star club
Are you coming down to ours this summer buddy?

Gostek

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Events Organiser
Events Organiser
Ok.... There is always something new... If the car wasn't shaking crunching etc it should be ok, but in this case shouldn't your rear diff lock?? I'm rly tempted to put pulsar on brake rollers now but I don't think it'd like it...


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Gostek

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Events Organiser
Events Organiser
@ROB_IOW wrote:Are you coming down to ours this summer buddy?  
It would be nice to visit IOW this year and we haven't got many holidays planned this year so I guess I'll get Bea to get in touch with Marie and organise something Smile


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Mr B

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gtir technician
gtir technician
@johnny gtir wrote:Would say no as don't you need all 4 wheels independent so how would you get the potable roller under the wheel where the mot roller is or am I picking this up wrong ?
Portable roller goes on axle not in test bed, you just place them in front of non tested axle wheels before fully driving in roller bed, this system is used in may countries and similar is used for awd function testing.

Pulsar will be same scenario as robs evo, driving both wheels same direction will want turn prop so either try hopping out rollers or stress centte diff

Driving lsd diffs in opposite direction also not good for prolonged period,
Mot guy right when saying driving in opposite directions cancels prop rotation but that only safe on open diffs really and as can't really do proper full brake testing like that best doing manual road test to save hassle/problems.

Cosmic73

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If the car has a haldex or torsion diffs i wouldn't want the wheels spinning in opposite directions for long periods
Haldex is a hydraulic pump working backwards so the pressure generated would be high,
Torsion are mechanically connected worm gears, so they would be spinning around their diff pins trying to cancel out the speed differences (at equal speeds they don't turn)

Thing is this is not a +ve to +ve speed difference which they are design for, but -ve to +ve speed difference which maybe outside their design limits.



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