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Pricey Rising Rate Linkage

Blog Date - 28 November 2016

In case you don't know...what is rising rate linkage? On some monoshock motorcycles the shock absorber is not directly connected to the swing arm. Rather it is connected to some complex linkage such that the suspension changes from being linear to progressive.

The suspension is bolted directly to the swingarm on linear setupsThe shock is bolted directly to the swing arm on a linear setup.

A progressive suspension linkage on a motocross bikeRising Rate or Progressive suspension runs through several connecting parts.

Progressive? On a linear suspension system if the suspension is under a load of 100kg the rear of the bike may, for example, move 2cm down. If the load is 200kg it will move 4cm. 300kg? 6cm, you get the idea. Progressive suspension moves less as the load increases so at 100kg it may move 2cm as before but with 200kg it may move 3.5cm and with a 300kg load it may only move a little more, 4.6mm 

Why would we want progressive suspension? I'm going to a HUGE over-simplification here. Small bumps are better absorbed with a soft spring and bigger bumps require a stiffer spring. Linear suspension is a compromise, kind of hard enough for big bumps, sort of soft enough for small bumps but not ideal for either. Progressive suspension can be soft for small bumps and hard for big bumps at the same time. Wonderful! 

Erm...hang on there cowboy. Nothing is for free and the cost of this lovely progressive suspension is complexity. A standard linear set up has a big fat shock absorber and spring with one end bolted to the frame, the other to the swing arm directly. Simple, easy, cheap and requires very little maintenance other than the odd clean. To achieve progressive suspension manufacturers use a set of linkages with very clever angles and geometry between the shock absorber and the swing arm. This in itself costs money to create adding to the price of the motorcycle. 

The rusty and dirty twin shock setup of Rens old 125While twin shock setups lack finesse they're good enough for ordinary people, cheap and easy to replace.

So maybe it's only a few quid more, for all the advantages of progressive suspension it's worth it. You sure? Those linkages have bearings to keep the suspension nice and smooth. Those bearings have flimsy little rubber seals to protect them. Those bearings and seals sit at the bottom of the bike near the rear wheel. Those seals get covered in dirt and grime and rain and road salt. Those seals fail. Those bearings fail. 

Those bearings and seals - in my experience - tend not to be cheap off the shelf items. Those bolts through the bearings - in my experience - tend to be seized solid and require cutting out. Those bearings - in my experience - are a bitch to press out. 

So we have the advantage of super clever suspension versus the disadvantage of additional maintenance, hassle and wear. Is it worth it? In my opinion - no, nope. Having ridden twin shock, linear monoshock and progressive monoshock set ups I firmly believe the difference on the road under normal conditions is so so marginal that only the very best riders will be able to utilise any advantage of progressive setups. I think manufacturers would do better to spend the additional cost of linkages on improving the quality of the shock. Price for price I'd prefer a quality shock over fancy linkage. 

The monoshock on a DB5R bimota has no linkagesBimota didn't feel the need to fit linkages to their DB5R.

Take my CB500X. The CB500X, CB500F and CBR500 range are - let's face it - budget bikes albeit quality budget bikes. You'd be a fool to claim the X is the most capable dual purpose bike or the R to be the most sportiest sports bike. People like myself who buy mid range mid budget motorcycles generally don't go track racing. So why would Honda put progressive suspension on them? The much more expensive and considerably more powerful CB1000R doesn't have progressive linkages and having ridden one it certainly doesn't seem to need them either. There's nothing wrong with the handling on the CB500X, I doubt there'd be anything wrong with the handling without the linkages either. 

Perhaps the design and layout of all the parts require the shock to be moved lower and the linkages allow this? Meh. If Honda can't shuffle things around to accommodate a shock then they ought to throw in the towel and focus on making cars for pensioners and robots that can walk. Perhaps it's a secret ploy to generate future business. The linkage bearings will last the 2 years of a warranty then fail which means Honda can sell expensive non standard bearings and Honda dealers can charge a small fortune to fit them. To support this conspiracy theory just look at the lack of mudguard to protect the linkages. 

That's the second time this week I've gone all chem trails and they're out to get us. Is seeing the world as one big conspiracy and becoming paranoid part of getting old or am I just hanging out with the wrong people?

Addendum

Looking on Lings Honda's website the bearings for a 2015 CB500X cost

  • Dog Bone(Connecting Bar) has 2 needle bearings 17x24x30mm £14.37 each £28.74
  • Dog Bone(Connecting Bar) has 2 dowels within the bearings £17.48 each £39.46
  • Dog Bone(Connecting Bar) has 4 rubber seals 17x24x5mm £5.85 each £23.40
  • The swing arm has one non-descript needle bearing £21.25
  • The swing arm has 2 rubber seals 17x24x5 £5.85 each £11.70
  • The swing arm has 1 dowel within the bearing £17.48

Total cost = £142.03. AYE CA-RUMBA! £142 for 3 bearings, 3 dowels and 6 seals. 

There is also a needle bearing in the bottom of the shock - £21.15, a dowel - £17.48 and 2 more seals - £5.85 each. I've not included these as a conventional linear setup also would have the same bearings that would wear out just as quickly. Still to fully refit the entire rear suspension bearings would come to £192.36.

A piece of plastic zip tied to the swing arm protects the costly bearing on Ren's 500My hack to protect the costly bearings from the worst of the road spray.

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Reader's Comments

Stuart said :-
Another interesting article but to take it one step further what about buying a 5 year old bike that has reactive suspension (when it is controlled by a computer).

Would it make me a better rider in the first place? I think not as I'm sure I don't get anywhere near the limits of the bike as it is and then if the system has been neglected and bathed in salt and road crud how much will it be to fix that?

Give me good old fashion suspension any day!

Stuart


28/11/2016 20:59:58 UTC
Ren - The Ed said :-
Cheers Stuart. I hadn't even considered reactive suspension, I dare not think how much that sort of thing would cost to replace.

There's a great deal to be said for simplicity. Of course a fully reactive, digitised, programmable, progressive suspension will be better than an old twin shock set up otherwise Rossi and Marquez would be using those. But then they have a whole team of top flight engineers to look after their bikes and they're only used a few weekends a year on unsalted and for the most part dry roads.

So...twin shock...carburetted...points...single cylinder...air cooled...steel frame... Come on Ian Soady, which vintage machine to we really need?
28/11/2016 21:38:50 UTC
Doug said :-
One of the many reasons I replaced my stolen Enfield with...

...another Enfield :-)
28/11/2016 22:40:36 UTC
Ren - The Ed said :-
Quite agree Doug. The Enfield does have fuel injection and digital ignition primarily to allow it to meet stringent modern emissions regulations, other than that I can't think of a simpler more work-onable modern machine.
29/11/2016 07:23:06 UTC
Ian Soady said :-
Of course, my Sunbeam has no rear suspension at all so should suit you down to the ground. As well as very low (but adjustable) seat height, light weight (around 250 lb - say 120 Kg), girder forks with virtually no damping, no electronics or electric start, no disc brakes to seize up in the winter (well TBH virtually no brakes at all).....

But I couldn't really recommend it as an everyday machine. I'd actually go for something like the one in the link below.

Interestingly WRT active suspension, my Land Rover Discovery has Active Cornering Enhancement which is a very clever way of stiffening up the anti-roll bars using signals from accelerometers and a little computer so it corners absolutely flat rather than wallowing about. It also knows when you're off-road so switches itself off, progressively stops working when cornering g exceeds 0.4g and locks itself in the case of severe side slopes. It's been working with no problems for 16 years and 150,000 miles, so electronics don't have to be unreliable.......
www.carandclassic.co.uk/car/C803028 ...
29/11/2016 10:27:45 UTC
Ren - The Ed said :-
CB250RS? I know these machines were much loved back in the day but I also know they had something of a reputation for eating their cylinder heads. Anyhow Ian this model would have CDI which is a black box which you can do nothing with.

Electronics are peculiar. For myself the thing I don't like about electronics is you can't see them working. If the con rod is poking out your engine "thar's ya problem." If the brake hose is cracked and leaking "thar's ya problem." With electronics you can't look at a engine temperature sensor and see that it's no longer producing a 7.5 ohm resistance at 90 degrees C. You can't hold a crank position sensor in you hand and feel if there's any play in it.

But they are more reliable than say points. Many cars and motorcycles can cover far in excess of 100,000 miles without EVER needing adjustment or replacement of the ignition timing setup. But that day when it does stop working you can't get a file and a feeler gauge out to get you going again. Pros and cons.

Mind you, you can't plug a small computer into a points system and have it tell you that there's a lot of resistance on plug number 3's low tension circuit. Pros and cons.

When I look at the injector throttle body on the CBF125 it is actually much simpler than a carburettor. See the link.
www.bikesandtravels.com/biker.aspx?ride=750 ...
29/11/2016 11:05:13 UTC
Ian Soady said :-
You're probably right about the CDI but they're very simple circuits to make up and they're all over the place - mowers, pit bikes etc - and it shouldn't be hard to find one that would do the job. Yes, I do seem to remember tales of head problems with the RS250 but at 6,000 miles that one should be OK.

I have to say after many years with points I prefer the electronic version - I had Boyer ignition on the Commando, replacing the original points, and it was much better. And remember you still have a capacitor and coil (whether in a magneto or freestanding) with a points system - unless you're talking about a veteran's hot tube, which I guess you aren't. Capacitors are impossible to test properly and all you can do is replace them. CDI doesn't need them.....

I do agree that points will probably still keep working even when they're nearly worn out whereas electronics tend to just die on you. I have a little black box that I plug into my Discovery and it tells me exactly what's going on so that I don't need to replace bits in the vague hope that I've found the problem. Everything else just needs a bigger hammer.
29/11/2016 12:21:51 UTC
Bob said :-
CB250RS - I had one and I wouldn't have another. The rear cush drive arrangement is totally inadequate and ends up eating the hub. The camshaft ate itself when a lump of hardened surface fell off. The cylinder head cracked right across the valve seats of the LHS inlet and exhaust valves and up the spark plug threads.
Mix in failing cam chain, squeaking clutch and flailing balancer chains.
Good luck....
01/12/2016 12:31:00 UTC
Ren - The Ed said :-
Having scanned the forums regarding the CB250RS it seems a very "marmite" bike Bob. Some speak exactly as you do, unreliable and prone to serious self destruction. Others praise it's handling, performance and indeed longevity as long as the oil is changed often. I just find it hard to believe it had 33bhp from 250cc back in the day. It must have been one overstressed motor.

I've never had points on a bike or a car Ian and while black boxes do just die with no warming I'm with you...CDI or Digital Ignition overall is probably better than points.

CDIs can be simply swapped out and as long as they're not too costly that's fine. Bob's got it sussed, he's got spares already. Digital systems can be too...unles...there's an immobiliser in there too. Then you're in a whole world of pain and price.
02/12/2016 10:11:22 UTC
Bob said :-
CDIs are a necessary evil I feel. I've run many bikes over the years and I've had many points related issues. They were all fixable of course, but I've never had a CDI go bad.
On holiday runs I pack a spare CDI just in case. As I've opined on here many times, FI is for me a step too far....
02/12/2016 10:34:14 UTC
Ian Soady said :-
Yes, enthusiasts for points always say "Yes, but you can fix them by the roadside". My reply is "with CDI you don't have to".

Although having said that, although I said the Boyer I had on the Commando was fine, there was one occasion when the Norton was coughing and spluttering. Of course in La France la plus profonde.....

After stripping the carbs twice to no avail I realised that the cause was a poor connection to the Hall effect triggers due to a crimped pre-insulated connector. I've never used those horrible things again, preferring solder - although again the naysayers tell me it will do all sorts of terrible things to the cables.

It wasn't helped by the Norton isolastic system which to the rider feels incredibly smooth but at the expense of all the mighty vibration from an 828cc parallel twin staying in the power train.
02/12/2016 12:11:38 UTC
Ren - The Ed said :-
I dunno Bob - I'm sure we could find space for a spare computer...throttle body...oil temp sensor...air temp sensor...mass air flow sensor...crank position sensor...throttle position sensor...water temp sensor...lambda sensor...oh and a diagnostic PC to reset and reconnect everything.

I too have been told in no uncertain terms that soldering connections on a motorcycle is a big NO NO! Apparently, allegedly solder it brittle and it could cause the wire to snap. Yeah...I can see that...I've never experienced it but I have experienced crimped connectors working loose. You won't be experiencing any vibrations on the CB400 Super Four Ian. Smooooooooooooooooooooth as the finest silk.
02/12/2016 16:39:10 UTC
Ian Soady said :-
Well I've been soldering cables for over 40 years and never experienced this brittleness.

I think failed solder joints are almost(?) always due to poor technique. Instead of getting the components hot enough to melt the solder so it flows, many people try to "stick" things together by carrying the solder on the iron to relatively cold components. Another common error is to put far too much solder so it tracks up the wire and maybe causes the brittleness people speak of.

I remember reading about soldering cables on aircraft and one of the criteria was that each strand of the cable should be clearly visible but coated by a thin layer of solder. This allowed the strands to be counted - if they weren't all visible the joint was rejected. I'm afraid mine don't quite come up to this standard but I do try......

I do think proper crimped connectors are good and indeed may be better than soldering but this is when they're done with proper materials and equipment - not those horrible little pre-insulated jobs squeezed with an old pair of pliers.
03/12/2016 10:14:46 UTC
Ren - The Ed said :-
Well I'm in the soldering camp. The connector on the reggy reccy on the CBF125 was looking way past it's best and the wires had been rubbing on the panel too. As such I've attached them cheap and nasty spade connectors with solder and re-routed the wires a little.

Pictures to follow in another article. In the mean time I've have reached a decision. I hate allen bolts. One's just rounded off in a futile attempt to remove the deceased stator. I'm having a brew to calm my nerves before attacking it with the Dremel.

Again - wish me luck.
03/12/2016 12:45:28 UTC
Ian Soady said :-
If you hate Allen bolts (or socket head screws as we usually call them ;-) then you're obviously too young to have suffered those dreadful cross-point ones that used to hold Japanese bikes together. Made out of something like case-hardened cheese - how they were ever tightened up so tight beats me. Not helped by the fact that they are a weird local standard - JIS - which is superficially similar but in detail crucially different to Phillips (and of course completely different to Pozidriv).

You can often get a burred socket head screw out with a slightly bigger Torx bit - which I actually like although lots of people don't.
03/12/2016 13:19:38 UTC
Ren - The Ed said :-
Oh Ian, I am indeed old enough to remember the cheesy crosshead engine case "bolts". I've spent many an hour with a hammer and knock through sharpened screwdriver trying to release such things. I suspect the factory actually forged them in situ as that's the only way they could be so tight.

CB250 Dream, 1978 model. CD200 Benly 1985. Honda H100A. Ah such sweet memories, the sight of blood mixing with dirt and oil, happy days.

I did pop in a torx, to no avail. Dremel did the job of removing the head and the remaining stud came out as if it had never been tightened. I have since spent another hour or two cleaning and prepping everything for the hopefully imminent arrival of the replacement.
03/12/2016 19:13:44 UTC
Bob said :-
I thought I'd read somewhere that those infamous cross head screws of the 70's and 80's were neither Philips nor Pozidrive, rather they were some Japanese standard. Of course nobody ever had the correct screwdriver and this was the reason they caused so much trouble.
I note that the MZs and JAWAs that I've owned employ slot cut cheesehead screws throughout - you can get them undone with virtually any screwdriver.

I did enjoy my CD200 Benly, lovely little bikes!
05/12/2016 12:16:31 UTC
Ren - The Ed said :-
You're right about the weird spec on the crossheads, see Ian's post. They were apparently JIS which probably stands for Japanese Industry Standard. Or perhaps the original term was in Japanese.

OH the Benly, the sweet, economical, hilarious, wonderful CD200 Benly. I despatched on mine for a while, ran it up to about 70,000 before the crank went. That was my fault I was using cheap thick oil and the crank needle bearings don't like thick oil. I'm told the thick oil forms a ridge in front of the needles leading to cavitation or something like that.

I saw one at the Manchester Bike Show a couple of years back and my heart melted. There's not many left now.
05/12/2016 14:48:08 UTC
Alan said :-
I was going to buy one of those back in the 80's for when I was hill walking on my own during the week when my mates were at work rather than run the car. back in the days when your car license covered you up to 250cc as a learner. Was about to fork out my hard earned cash when the dealer asked if I had a full license. No says I. Can't have it then he says, they changed the regs, you can only drive a 125. I was heartbroken. It was the ideal bike, good mileage, comfortable, nice looking not at all flashy, reliable and powerful enough to make a decent speed heading into and through the Highlands loaded with walking and camping gear.
19/12/2016 11:45:06 UTC
Ian Soady said :-
My dearly beloved wife has bought me a set of Vessel JIS screwdrivers for Christmas! Pity she won't let me unwrap them yet as I spent an hour yesterday cursing some self-tappers on the Discovery.......
www.onlyqualitytools.com/catalog/Vessel/9303.html ...
19/12/2016 15:01:26 UTC
Ren - The Ed said :-
Alan - are we talking about the CD200 Benly or the CB250RS? I can't say I am old enough to have ever ridden a 250 on "L" plates, those days were gone in 1989 when I first threw a leg over a bike. I had a Honda H100S. I thought it was ace but then I didn't know any better. The Benly was my first "not a 125" bike after I passed my test and I loved that dearly too.

Ian - your wife spoils you. Prey tell what have you purchased for the lady in return? I do hope it's a set of rainbow coloured hex keys. Oh she'll be thrilled to bits!
www.onlyqualitytools.com/catalog/PB_Swiss_Tools/Rainbow_Ballpoint_Hex_Keys.html ...
19/12/2016 16:32:14 UTC
Alan said :-
The Benly.
19/12/2016 17:46:53 UTC
Alan said :-
Don't forget the matching screwdriver set.
19/12/2016 18:15:38 UTC
Ren - The Ed said :-
Mrs Soady is going to be overwhelmed this Christmas. Allen keys, screwdrivers and all in rainbow colours. She's a lucky lucky lady.
20/12/2016 07:18:37 UTC
 

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