Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Knackered AVOs

With the dreadful cheesium bubblegum bushed rear AVOs replaced with a nice set of Bilsteins some time ago, the front AVO coil overs on Monty's Mulfab front wishbone conversion have been on my hit list for some time now.

Excuse my colorful language, but hopefully this helps explain why I'm not a fan of AVOs.

https://youtube.com/shorts/ON39PIPXBR0?si=Vabu6cpfak3Hsjan

Monty's very dead AVOs had only done 10,000 miles before the bushes failed, and just another 5,000 miles to start leaking.

Let's try a nice new pair of custom built adjustable twin tube 400's from Protech

Totally agree on the AVO's

I've put my head over the parapet before regarding their quality (and dampers an a Mog aren't even worked hard)

Tim at Protech was very helpful today, I'd arranged to drive down to their facility and remove the AVOs so they could be comprehensively measured and then tested on their sophisticated suspension dyno, a friend and I had the old leakers off the car in 15 minutes, we then handed them to Tim before heading off for lunch at a nice local pub.

While we were out stuffing our faces Tim and his team measured the old AVO spring and damper rates specified by Peter Mulberry when he created the Mulfab front wishbone conversion, and built a brand new matching set of their twin tube adjustable 400s. I went with bonded rubber bushes rather than rose joints, I also specified a full black anodised finish for additional corrosion protection, finally my preferred ride height was also replicated before we fitted Monty's new custom set of Protech coil overs.

Including driving down to Protech and back home, the whole exercise was completed in a day, Tim couldn’t have been more helpful and that drive home proved Monty's front end is greatly improved. The Protechs have 14 clicks of adjustment, we started at six clicks from zero, then tried eight clicks, unlike the Gaz Gold Pros on my TVR you can really feel the difference of each click.

It's only day one, but as you might expect given the state of Monty's old AVOs, the difference is night and day! Only time will tell, but Protech have a good reputation and do seem to stand by their products with excellent after sales service. l'll I report back here on how they perform (and last) on Monty the Morgan who is driven enthusiastically on both road and track, and in all seasons.

+1 for protech .. ran them on my Single-Seater racecar ... they'll valve them up for you to suit your requirements.

K

Excellent Image

I’ve never used Protech before, but coming from the TVR world I've many friends who have, and generally their experience with the company and their products has been very good. For a period of time, I did run Gaz Gold Pros on my Chimaera from Protech’s main competitor Gazzmatic Suspension, but I didn’t get on with them so I went back to Bilstein which were excellent.

I would have liked a set of Bilstein coil overs on the front of Monty, but Bilstein only work with re-sellers, this would have added time and complication for the custom coil over build required for Monty’s Mulfab front wishbone conversion. Protech made this process incredibly easy, within just a few hours the old AVOs were thoroughly appraised, measured and dyno tested before the perfect set of custom Protech 400s were built for Monty by Tim.

Counting the clicks yesterday proved my single adjuster Protech 400s (bump & rebound are set with the same adjuster knob) shows I actually have 13 settings available in total. However, from previous experience of adjustable coil overs click 1 & click 13 should be avoided, so in practice I have a range of 11 clicks to work with which is proving plenty.

Tim at Protech recommended 6 clicks from soft as a good mid-way starting point, I did a quick down and dirty static bounce test at the recommended 6 and felt I could go firmer, so set them at 8 clicks for the drive home. This seemed to work well, if a shade firm, so I've been going one click softer at a time and then testing the effects on my favourite back road where I know every turn, dip, camber change and break in the road surface like the back of my hand.

Monty became quicker and quicker each click I removed, so a more compliant setting is definitely what the car wants, interestingly the firmer setting of 8 clicks I started out with had a negative effect on the rear, my guess is a more rigid front end setup was passing more torsion loads through Morgan’s rather flexible traditional chassis that ultimately could unsettle the rear as the car moved at pace over rougher road surfaces.

I've now ended up with what seems to be the halo setting of 5 clicks from full soft, this with the brand new 275 lb springs that I suspect still have some settling to do. A setting of 5 clicks seems quite soft to me, but it's absolutely what the car wants. At 5 clicks Monty has never covered ground so quickly, and on my favourite back road I can confidently say he's noticeably quicker than my old 4.0 litre TVR Chimaera that had 238 horsepower and 260 lbs/ft of torque.

Monty runs Bilsteins on the rear from SSL which are doing a great job considering the design limitations of the live axle, and Morgan’s rather ‘interesting’ attempt at fitting telescopic dampers. I appreciate much has already been written about why the rear suspension on a modern Trad Morgan has issues, but the very limited travel aside, to me one of the mistakes made was the damper eyelet orientation chosen my Morgan.

The arrangement is clearly fighting itself, there must be some horrible twisting forces going on because the way they’ve been fitted means the dampers can’t pivot and swing with the axle as the leaf springs flatten, quite simply the eyelet orientation is 90 degrees wrong. Clearly there’s the potential for some serious stiction, and I wouldn’t mind betting this means on sudden load there’s some momentary damper lockup briefly sending the rear end into hardtail mode, which is the true source of the spine jarring experience we all know and love.

Anyway, I digress, what I’ve proved with my Protech front damper setting experiments on Monty is, a more compliant front end definitely helps (if not cures) the situation at the rear.

Dave.

Montegue

Get on to Cain's site, wolf performance and for £28 he sells a set of realignment top end mounts for the rear shocks. Instead of them being cranked over to the top of the rear hoop they can be positioned to the vertical and this makes a far smaller arc when the springs are flexed and stops the shocks destroying the rubber mounts as well!

Thanks Sewin, I assume you mean this top bolt and spacer kit?



https://www.wolfperformance.co.uk/product/rear-damper-top-mounting-kit/

If so, I created my own custom spacers and sourced my own 7/16" high tensile bolts some time ago, but this doesn’t solve the fact that the damper eyelets need to be at 90 degrees to their current position so they can pivot with the axle as it swings backwards on the spring's swing shackles.



As we can see Monty is riding on his 30mm Bilstein bump stops.

However, the current thinking is, if I fit Roger's spring assisters and adjust them correctly I can delete my Bilstein bump stops and gain 30mm of free damper travel, well, probably more like 25mm to be on the safe side.



Saying that, even on the current arrangement and despite running on the Bilstein bump stops, I do have what I'd describe as sufficient travel.


The very squishy compound the Bilstein bump stops are made from certainly helps here, as does their cone shape which makes them very progressive.



I must stress Monty actually handles extremely well as is, but there's is still the very occasional typical modern Trad Morgan bottoming out condition I'd like to eliminate, and Roger's spring assisters seem like they may be worth a try?



I’m currently in discussions with Roger to see if his above kit will fit on Monty?

I'd be very wary of deleting the conical bump stop (not sure about Bilsteins) but some others bust the internal workings if they bottom out on full compression

AVO's certainly do

Montegue,

Yes I agree with you re. the 90' orientation required on the upper mount. How much better would the shock's last/perform if the rotational elements were in the same plain rather than trying to bend the shock absorber longitudinally. Should have realised you might have already addressed the vertical orientation to reduce rotational forces though. Silly me!

I have Spax adjustable shocks as supplied by SSL on the rear of my car and Rog's assisters. Went for the SSL option as I knew they would have the correct open/closed length, and I find that to be as good as I can get with the standard set up. If buying now I would go with Cain's new to the market shock's. I can't remember how many clicks up from softest setting I have but seem to remember that it's about half way, There really is a sweet spot which seems to-jump out at you when you hit the right setting for your car, I found that easier to find stepping up from softest setting rather than dropping down from the hardest setting as stepping up you can easily identify that click up that changes it whereas dropping down you notice a change right through the middle third of the range and I found it difficult to know where to stop adjusting but on going up it was obvious. I have about 34mm static unloaded spacing between the adjusted assisters and top of the leaf spring with the car on the ground and it really has made a huge difference in ride quality. The contact mark on the top of the spring is about the size of a 1P coin so I figure I'm only just using the helpers in slowing that final level of compression to the springs.

I do get what you're saying, however in theory with Roger's spring assisters set correctly the damper should never fully close, and on a suspension system thats clearly so desperately short of travel, the 20mm or so of additional compression travel released by removing the damper bump stops would be very welcome indeed. The recommendation to delete the bump stops actually came from Rog himself, but with the caveat that the distance between the elastomer cone and leaf spring must be set very carefully.


I also bought my Bilstens from Dan White of SSL, so I'd also assumed he would supply the correct open and closed lengths, however as we can see I'm running on my bump stops.



In Dan's defence I am running 20mm lowering blocks and BCC anti-tramp rear springs, the Bilsteins actually have a very large operating range from full compression to full droop, the issue to me seems to be the distance between my bottom damper fittings mounted to the brake drum back plate/axle, and my 7/16" top damper mounting tubes welded to the hoop.

I believe the distance between the damper mounting points was reduced by 20mm when I fitted the 20mm lowering blocks, it also looks likely the BCC springs may have played their part too by stealing another 5 - 10mm? The result of losing up to 30mm of travel is I now only have 30mm left to work with, but that's all taken up with the big 30mm Bilstein bump stop.

The truth is I've been aware of all this for a long time now, the original plan was to raise my top damper mounting tubes by 30 - 40mm to win back the lost travel, but before getting around to doing this I broke the hoop off their brackets. The original Morgan welds were poor and the whole thing is much stronger now, but the underlying issue remains. I had asked my fabricator to raise the hoop when he welded it back in place, and while he did attempt to do so I really don’t think he could have achieved much (if anything) by way of a hoop lift.

This brings me full circle to my original plan of raising my top damper mounting tubes by 30 - 40mm to win back the lost travel, I then plan to fit Roger's spring assisters, adjust them as instructed, and ultimately delete the damper bump stops to finish off the job. Rog is currently studying some Monty measurements I've sent him, and is supporting me with his engineering expertise and Trad Morgan rear suspension knowledge.

Watch this space