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MG Midget and Sprite Technical - RTL, Speedo & Brakes

Just been out for a run in the Sprite for the first time in quite a while & i have broken my re-calibrated Speedo, the needle now rests on the wrong stop, the speedo cable has also snapped at the gauge connection.
My Mumford link has overcentred & locked the back end solid. When i set it up i had the car on jacks & the axle floating, should i have put the weight on the axle instead?
The big brakes are staying on which i think is an air lock in the servo, the calipers are new as is the master cylinder.
Lastly i'm getting an oil temperature of 105-110 after a bit of WOT usage, normally around 90-ish, is this alright? I'm using a 13 row oil cooler with a thermostat.

Any comments gratefully recieved.

cheers
Brad
Brad (Sprite IV 1380)

This is a 100mph speedo you over speeded?

I wouldn't have thought you have an air lock in the servo.

I'd guess you have a 4 speed car if you regularly see 90 on the oil temp gauge? 105 is ok but costing you power. 110 is costing you more power and on the hot side. If you have a good synthetic engine oil I wouldn't expect 110 is a problem apart from the power loss. But, if those are the temps you see after a bit of WOT, what readings will you get after a lot of WOT? Where is the oil temp reading taken from.

Clearly a 16 row cooler will drop the oil temps.
Daniel Thirteen-Twelve

Brad,
My brakes dragged once when a new master cylinder went on because there wasn't enough 'slack' in the push rod from the pedal to the master cylinder...as things warmed up the slack (enough to 'rattle') ensures that the brakes don't drag.

A quick fix is to bung a couple of washers between the MC mounting flange and the pedal box...if that cures it then something more elegant can be done later.

A locked mumford sounds nasty, shorter check straps and a bit of fiddling required?


Rob
robnrrugby

Daniel,
it's a T9 box, with the oil temperature sender in the sump, when i say a bit of WOT, thats probably an understatment, the run was about 120miles on quiet A-roads. I've got a Smiths 120mph speedo in the garage that Speedy cables will be getting soon for a re-cal.

The brake binding problem doesn't happen if i disconnect the servo vac line, from reading in the archives i think i've air in the valve. It was occassionally binding before the master cylinder & caliper change.

Rob,
it may be just me but the locked RTL wasn't that bad to drive, a bit edgy & harsh but great feedback!
I removed the check straps for the rear shock conversion, maybe have a look at putting them back on, though i think the problem is when the axle is under compression.
Brad (Sprite IV 1380)

You should set up the RTL with the suspension loaded normally - otherwise the rods will cause the pivots to rotate as you lower the car, and there is a danger of locking, as you've found out.

Frontline delivers its RTL pre-adjusted and ready to fit to avoid these problems; in fact I think Tim recommends you don't bugger around with it despite their being adjustment on the pivot points and rods.

Your oil temps sound similar to mine (much the same of A as well as K):

90 on slower main roads
95 on faster main roads
100-105 on DC and motorways constant 70+ (where allowed)
105-115 on track-days (actually it goes off-scale since I use a capillary water gauge... Once at 'Combe it was getting close to the bump stop, with near complete rotation. Cooled down quickly when lifted off for corners - 2 to 3 C in <10 secs!

I don't have a cooler. It sounds like your cooler isn't doing its job, e.g. is there air-flow through it? Where is it positioned? Or does the stat really open? Try removing the stat and seeing max temp under your most extreme conditions.

A
Anthony Cutler

Welcome back, my suggestion would be to drive within the legal limits and not put poor BES through such testing.

No wonder you spend more time under the car instead of driving........

Would be interested in seeing your front spoiler though.

PS Did you get the replacement bolts made.

Shaun

Shaun

Ant,
my gauage only goes up to 110, i blame the blue Alfa 147 for getting in my way, i've a feeling he may be trading his car in soon as he obviously wasn't very pleased at being overtaken when he was trying so hard to out corner me :-)
The cooler is in front of the radiator with a Mocal thermostat fitted & it is connected the correct way.

The problem with the Mumford is at full spring compression when the axle is on the bump stops the RTL is near the bind point, also what doesn't help is the axle bolts i've used are too weak & have bent to the shape of a nanna, so i've a mate who owns a machine shop making some from EN24 bar stock at the moment, that should be strong enough.
I do need to restrict the upward travel of the axle to prevent a re-occurance, not sure how to do this easily yet, any suggestions?

Shaun,
i was within the legal limits 55mph, gravity just took the needle to the wrong stop, bit like my mini cooper.
I've a set of bolts being made for you too, it'll cost you a packet of chocolate hob nobs for the machinist.

No spoiler yet, but i have a few ideas after re-reading my copy of race car dynamics, though the Triumph needs to be finished first, tripple DHLA's can't wait :-)
Brad (Sprite IV 1380)

Could try sourcing some progressive polyurethane bumpstops?
l snowdon

Does such a thing exist?
Brad (Sprite IV 1380)

Brad

Sounds like the 2 main arms are too long; are they adjustable?

a
Anthony Cutler

There might be somethiong suitable in the Polybush range that could be adapted.
l snowdon

Ant,
the arms are adjustable though i set them up when the axle wasn't under load which i think was a mistake. I'm thinking of putting an ali pad under the contact area for the axle bump stop to restrict the upwards movement a tad as the other option is to remount the Mumford which is a pain.
Brad (Sprite IV 1380)

Bad idea after reading RCVD, i think the spring isn't helping as it resembles a flattened McDonanlds M, also the rear dampers were at 4 so i've upped them to 7 which is midway.
Also no air in the servo, though the brakes are perfect with it disconnect but stay on for a fraction with it connected (which really makes a mess of my apexes) anyone had the same problem?
Lastly speedy cables are sending a new speedo cable, with that i can do the calcs for the 120mph speedo & get that calibrated.
Brad (Sprite IV 1380)

This thread was discussed between 15/07/2009 and 20/07/2009

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