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Re: Mike's Cabrio Build
Got to buy this, well done Mike!
Got to buy this, well done Mike!
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- 9th owner of T693 SSC possibly a factory built Ford based V8 Sportster
- 4th owner of Q309 RNV, an early Cabrio built by Bob Copping, owned Doug & Liz Billings for 16 years
- 9th Custodian of JRR 929D, Triumph Vitesse based special Paul Moorehouse built prior to the Triumph Roadster kits.
- 8th owner of Roadster chassis number 2395. Now owned by Barry!
- Builder of chassis number 2325 (PKK 989M) in the mid 80's. Now owned by Eric & Lynne.Comment
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Re: Mike's Cabrio Build
Some days rank higher than others in the build of my Cabrio - today was an important one. I took it to a wheel alignment specialist to have the tracking and corner weights checked and optimised.
Mat Smith in Downham Market, Norfolk, came highly recommended.
He has worked alongside the kit car industry for 20+ years since his days at Sebring: he recognised early on how much a good suspension set up could affect the perception of a car, and has been specialising in suspension set up ever since. A lot of his work these days is in the TVR road and race community where he is well known for his knowledge and enthusiasm. After spending a morning at his workshop I can say he is my kind of tradesman - knowledgable and personable - a real find.
Mat took my Cabrio out for an initial drive, and reported back that he thought it drove pretty well "considering" - "considering" that I had only set up the tracking by eye, and tweaking a few things after a few quick trips around the block down our local farm roads.
There were some real surprises when he got his gauges on and the computer revealed the 14 settings: most of them pleasant, but two that were not.
In my readings about all things Cabrio I came to assume I would have a problem with the rear wheel camber and toe. This, I thought was going to be my biggest issue as the Cabrio's Sierra set up has no built in adjustability.
Surprise number one.
The rear set up was as close to perfect for a road car as could be achieved. Of the 6 rear readings all were Green, (within factory settings for a Sierra) and when reviewed individually we decided none of them could be realistically improved, so we left well alone!
This was a very pleasant surprise, my chassis must have been well set up in the factory jig. So, praise where it's due - and regular readers will know I am somewhat scathing of Marlin production standards - Well done Mark Matthews and his team.
The front was not so good........ out of 7 readings for the front, all were Red!
Toe and camber were close to where they needed to be (set up by eyesight) but were marginally outside of factory tolerances for the Sierra.
Caster, however, was a horror story!
For a road orientated car caster is recommended between -4, and -6 degrees to give quite strong self centreing, making the car stable in a straight line.
My near side reading : nearly 9 degrees
My off side reading : 13.5 degrees!
No wonder my steering was heavy!
The second ugly surprise was that my very expensive adjustable compression struts geometry meant that their adjuster nuts very marginally fouled on the bolt heads securing the location bracket to the chassis rails, and were not tightened sufficiently as a result. Essentially this is either a design fault by Compbrake who sell them, or the Cabrio chassis pick up point is not in the same plane as the original Sierra relative to the Track Control Arm height?
The solution was simple - take 3mm off the fixing bolthead to ensure clearance.
A further minor issue (not altogether unexpected) was that the compression strut on the off side could not be adjusted sufficiently to dial out the excessive castor (it became thread bound).
Again the solution was fairly easy - cut 10mm off the end of the compression strut threads! This sounds drastic, but is not when you think about it. I say this was not unexpected, as I know Simon Gregory (and I believe John Tootle) had the same issue.
So despite having "adjustable" Compression struts we had to remove them to remove the excess thread length, and then re-fit, and then re-run, the whole set up test again before dialing in the corrective changes.
It takes a while, even with correctly functioning adjustable Track Control Arms and Compression Struts, as adjusting each one impacts on all three tracking measurements - Toe, caster, and Camber.
Al-in-all it took around 2 hours to set up the suspension.
Then the really pleasant surprises were discovered.
Just out of interest Mat checked the corner weights of my Cabrio.
Overall weight with me in the car was around 1130kg (I weigh around 90kg)
The front to back split was 48/52% which was surprising given the cast iron 2.5 litre 6 cylinder engine I have up front. Almost a perfect weight split!
Mat explained corner weighting is almost impossible to set up perfectly at the tester's garage - the car's weight needs to be built into it as the build progresses: this makes sense. So Mat concentrates on diagonal corner aggregates being the same - thus making sure the car should behave the same turning right, or turning left.
My diagonal weights were 46/54% - not perfect, but in a road going car they are completely acceptable.
So, after 3 very interesting hours, I was able to drive back home. And how did it feel?
Transformed is perhaps too strong an expression, but the steering is so much lighter. Before, approaching a roundabout required mental planning, and Popeye-like forearms, and tight cheeks if travelling a little too enthusiastically!
Now a quick flick left, then right, then left, and I'm on my way - much more easily done, and so much more relaxed.
And the best bit, tightening up all the adjustable collars, and fully locking off with the set nuts has quietened the whole front suspension down remarkably. Previously my suspension was noisey, which I put down to the TCA, and Compression struts all being rose-jointed, and lacking any rubber/polyflex to absorb noise and vibration. Perversely tightening them up, and stopping them fouling on the fixing bolt heads now means the front end is much quieter.
I'm delighted with my day today -my Cabrio is back infavour.Last edited by Mike; 21-10-16, 09:47 PM.Comment
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Re: Mike's Cabrio Build
That’s really useful info Mike. When I tried using my new Sealey caster / camber gauge the front caster was off the scale i.e. more than 11 degrees! As I had bought the gauge for my classic I thought that maybe the steering geometry on a modern was not compatible with the Sealey gauge set up. Your checks make me think otherwise now. My Hunter has always wanted to go onto full lock when reversing which would tend to confirm that excessive caster is present.
You say that the rear toe was within limits for the Sierra but do you know what those limits are? Following an earlier thread by Derek Jones (excessive rear toe / rear tyre wear) I have recently finished shimming my rear hub carriers to get the camber down to 1deg-ve and at the same time did the final tweak to the rear toe to 1mm toe in each side. The original toe in figures were O/S 2mm and N/S 5mm! I remember noticing that the rear N/S toe on my old 2.0GL Sierra was also about the same so there’s something strange about the basic Sierra setting which may not read across to our cars as correct. Before I did the first hub shimming my rears used to scrub off the outer edge tread and need replacing quite often. Keep an eye on your rear tyre wear! Peter.Comment
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Re: Mike's Cabrio Build
Hi Peter
Have a look at this thread - I have reproduced the Ford data complete.
My results looked like this:
Top half is the BEFORE: note the Rear is all Green, ie within tolerances
The lower half are the AFTER set up - the rear was left completely as was.
Tracking Results 10.2016.jpg
My same setting results but shown with the specified ranges:
Tracking Results 10.2016 001.jpgLast edited by Mike; 22-10-16, 02:14 PM.Comment
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Re: Mike's Cabrio Build
Cheers for all the info Mike I will sort mine out when it is sprayed next week. I have the radiator out as well to resolve the running hot problem, and to engineer space for the air intake above the radiator. I also found that the fan was very tight when it was removed so that has been sorted as well.Comment
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Re: Mike's Cabrio Build
A great read thanks for postingMk2 SWB Marina Roadster with a 2.0L Pinto built in 1986Comment
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Re: Mike's Cabrio Build
Originally posted by cameronfurnival View Post
Thanks Cameron.
I wonder if we can obtain any other back issue Marlin articles that could be combined together into a thread of their own?Comment
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Re: Mike's Cabrio Build
Minor Update:
Those who have followed this build will remember I had to modify a collar/sleeve to make the imperial threaded Smiths Classic water temperature sender fit in the metric BMW head. Also the gauge was designed to operate on 10v supply. I was never happy with this, so contacted Caerbont Automotive to see if they could supply a gauge which would work with the standard BMW VDO sender on 12v.
This was the result:
Fuel Gauge - Digital.JPG
They used my own BMW VDO sender to calibrate it digitally to one of their Flight gauges : (they immerse the sender in a bath of oil, as it maintains a more uniform heat spread than water, then heat the oil and calibrate the VDO output via a software map to their digital gauge - so my gauge is programmed to my VDO sender!).
It now records actual temperatures within a degree or two, using a 12v supply.
Having fitted the gauge and sender last week I can report it works beautifully.
I wonder if they can do the same with the fuel gauge?????Last edited by Mike; 13-05-17, 06:37 AM.Comment
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Re: Mike's Cabrio Build
Hi Mike. Wonder if this could help?
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Re: Mike's Cabrio Build
Interesting Scott. I shall carry out a little more research.Originally posted by scott h View Post
My Smiths sender is designed to give 20 Ohms "Full", and 240 Ohms when "Empty". However in a shallow Cabrio tank, the float arm has to be shortened to such an extent (to achieve a full arc between Empty and Full) that the float is no longer heavy enough to overcome the senders physical resistance to rotating: not good as this overstates the fuel in the tank!
This Spiyda wizard would allow me to lengthen the arm, but compensate for the reduced range of sender outputs. Certainly a Plan B backstop.
Currently my Baldrick's cunning "Plan A" is to simply add a little extra weight to the float - I hope a small nut soldered on to the arm will help gravity do its job.
Like many of my little schemes I know the theory works, but will it translate into practice?Last edited by Mike; 13-05-17, 07:11 AM.Comment
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Re: Mike's Cabrio Build
Scott, you are a hero!
My gauge does not match the sensor in my tank and reads full all the time. I've been meaning to get it sorted but couldn't face the hassle of taking out the tank to get the work done. This solution is not cheap but it would probably cost as much to get my tank adapted for a new sensor and it saves all the bother.
Sorry for the thread hijack.Comment
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Re: Mike's Cabrio Build
They had a stand at Stoneleigh which is how I first heard of it. Be sure to mention this if you contact them, it can only be good for the show.Originally posted by JonW View PostComment
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