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Progressive fork springs

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Fred the Zed
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#16 PostAuthor: Fred the Zed » Mon Sep 09, 2013 8:40 pm

zorded wrote:Maxton Engineering
Laurel Bank
Kingswood
Frodsham
Warrington
Cheshire
WA6 6HX
U.K.

TEL : +44 01928 740531
FAX : +44 01928 740635


Thanks for your enquiry, we can help you out with the problem on your
forks but have no spec sheet for you to read.

We convert your forks, but not by modifying the existing internals. We
throw everything inside the fork away and start again with our internals.
The internals we supply is our own GP20 cartridge style damping system.
The cartridge system is the same type of internal as what you would find
in any modern front fork. It has been manufactured and developed by our
own engineers and has pistons and shim stacks for the rebound and
compression damping. The Cartridge also has needle valves so you can
adjust the
damping. The damping adjusters are external, so you can change the damping
without having to strip the forks down, but we hide the adjusters to keep
the classic appearance. As part of the conversion we also machine new
fork tops to take the new cartridges and damping adjusters. We also fit
new springs.

Every Maxton GP20 cartridge is built to order, the reason for this is to
valve and spring the cartridges to suit the fork, the bike, the riders
weight and what they are using the bike for. Once the cartridge has been
manufactured we then fit the cartridge to the fork to make sure it works
correctly. In most conversions we have to modify the original bottom
sliders and stanchions so our cartridge will fit and work properly. The
forks are then returned to you fully serviced with new seals and the
spring preload and damping set up.

The Maxton GP20 cartridge costs between £330.00 and £530.00 + V.A.T.
Depending on how adjustable you want the cartridge to be.

- for £340.00 + V.A.T the cartridge is adjustable for rebound damping.

- for £540.00 + V.A.T the cartridge is adjustable for rebound and
compression damping.

All adjustment can be made without having to strip the forks down.

To service the forks with new seals and install the cartridges costs
£140.00 + V.A.T. In some cases there are also charges for any extra work to get the forks to work correctly. In Norton and Seeley conversions we machine new bushes for both top and bottom sliders, the bushes are made from a hard wearing frictionless plastic called Delrin. The bushes cost an extra £80.00 + V.A.T. In some cases we also have to get the original sliders honed as the bore of the slider is not machined very well. The cost of honing the sliders is £80.00 + V.A.T for the pair. In some
Triumph forks the seal is held in place with friction on the outside
diameter. We machine a groove in the bottom slider, so the seal is retained with a cir-clip. This costs an extra £50.00 + V.A.T.

The cartridge conversion fits inside most forks with stanchions that have
an outside diameter of 35mm or bigger. In some H**** forks the stanchions are 35mm outside diameter, but the internal diameter of the stanchion is too small for the cartridge to work. For these forks we supply new Hard Chromed stanchions with a larger internal diameter. These cost £200.00 +V.A.T a Pair.

If you need any more information about the modification we carry out you
can ring me on the telephone number above, if you cannot get through fax
me your number and I'll ring you back as our phone can be very busy.

IF YOU LIVE IN A COUNTRY WITHIN THE E.E.C THEN YOU WILL HAVE TO PAY U.K
V.A.T, UNLESS YOU HAVE A TAX CODE FOR YOUR COUNTRY.

Regards

Richard
Maxton Engineering



Maxton kit is superb but they aren't a charity and you get what you pay for, but I was wondering if a cartridge fork internals from another production bike could be fitted into the original forks...... it would still be a massive improvement over stock.... any ideas?

Fred
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Al
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#17 PostAuthor: Al » Tue Sep 10, 2013 1:02 pm

That sounds like the perfect solution - apart from the cost!
I don't know whether anyone sells Race Tech products in the UK, but their "Gold Valve Cartridge Emulator" kits have a good reputation.
http://racetech.com/html_files/vintage_testimonial.html


They cost about $170, and Race Tech can supply springs of the "right" rate for about $125.
http://racetech.com/ProductSearch/2/Kaw ... 00/1977-80
It might be worth giving them a call to see what they can do.


Thanks Strebe. To answer youre question BT 45's at 31 front and 30 rear from memory as its been a year.
Have been using roadriders and at the same pressure or on track 1 psi less in both.
Put a BT45 rear on (secondhand) and had to go to 33 psi rear.


Race Tech have two distributors in the UK.
One is in Sheffield.
Luckily one of them is half hour from me and that where i have just been.
I took one fork leg in bits and they had a measure up and did some simple calculations.
They measured the spring rate of the existing springs as well.
Made a selection based on intended use and came away with emulators and 'Race Tech' linear uprated spring kit and 20W oil.
Spring kit was £94, emulators were £124 and oil £8 a litre.
VAT was extra.
Got a load of other things too whilst i was there.
http://pdq1.com/
Larry knows his racing and is in the process of re-building a Z1000R and making an ELR to race with for himself. Helpful guy and i can see me back there for various reasons.



Maxton kit is superb but they aren't a charity and you get what you pay for, but I was wondering if a cartridge fork internals from another production bike could be fitted into the original forks...... it would still be a massive improvement over stock.... any ideas?

Fred


Thanks for the input Fred i can see what youre getting at and falling off is something i intend to avoid if possible.
Dont know if you could use internals from later forks but i guess anything is possible. Internal diameter is going to be a real problem though i would have thought.
My choice may not be the correct / best one but i cant afford to Maxtonise my forks and simply replacing springs isnt going to help (ala Hagon progressives)
Changing forks to later ones was another possibility but i want to keep the original appearance wherever possible.
Turns out that those progressive springs are technically two step or twin rate. Take a look at the compression graphs in the workshop manual, it says it all.
A truly progressive spring looks different as was shown to me today.
Something like; varying material thickness, incremental gaps and tapered too.

AL
1981 J1

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#18 PostAuthor: KWACKERZ1 » Tue Sep 10, 2013 2:24 pm

Glad you have done something about those forks nice one,
Can pics of the bits before fitting. :wink:

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#19 PostAuthor: Al » Tue Sep 10, 2013 2:53 pm

Phil i have to say a very public thank you for all youre help so far. Its been an inspiration to me and to push through with changes and not give up.

Did the first two track days with one bent fork and then bought some others from Padders which are dead straight.
I mistakenly thought that the progressive springs in forks # two were the answer.
Cant believe i am still in one piece after Cadwell Park and Odiham and Donnington.

Yes will do some pictures but if you havnt seen emulators before you may have to get the glasses out.

Thanks again.

AL


From the top;
One bent fork leg.
Original linear spring 0.6kg/mm
Pair of 0.95 kg/mm race tech linear springs in bag.
Left;
Spacer tube to set static sag. (yet to be cut to length)
Right;
Old bottom leg (worn out)
Damper rod as standard.
Race Tech gold valve Emulator.
Alternative emulator springs for alternate uses in bag
Image

The Gold Valve Emulator is the tiny bit in the middle.
It sits on top of the damper rod and is held in place simply with the pressure of the spring.
It has a major and a minor diameter which if sized correctly holds it centrally.
It has a main valve (spring loaded) and a bypass.
Basically you drill out the original holes (to 8.5mm) in the very base of the damper rod and that renders them useless.
The emulator then takes over what they used to do.
The central (main valve) in the emulator is infinitely adjustable and you can adjust / re-set it by lifting out the springs and pulling it out of the top leg.
No need to drain the oil. etc etc
No shims its done on the number of turns.
Not really technical like Maxton and new bike stuff but for someone who didnt realise he was riding around with a bent fork leg, more than adequate.:shock:
Image

Alternate 'Race Tech' agents /distributors.

Shock Tech
Last Updated by RT on Mar 31, 2011
40 Aylesbury Crescent
Wincobank Sheffield S9 1JR
United Kingdom
0114 243 4226
Contact: Ryan
RYAN@SHOCKTECH.CO.UK
Dirt, Street, ATV
2 mins from Meadowhall, Junction 34, M1
Last edited by Al on Tue Sep 10, 2013 3:45 pm, edited 2 times in total.
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#20 PostAuthor: KWACKERZ1 » Tue Sep 10, 2013 3:30 pm

No problems its what the club is all about!

Don't worry about the pics Al, have just rummaged through their catalogue.

I think you may have found a better solution for me for the GSXR bottoming out problem, just need to find the cash now.

Cheers
Phil

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#21 PostAuthor: Strebe » Tue Sep 10, 2013 10:18 pm

Al, I'm pleased that you have found a good solution. It would be good to hear how the bike handles once you've got the new parts fitted.
Thanks for the details of the two RaceTech suppliers - I'll be paying a visit to PDQ. The prices seem pretty reasonable.
Coincidentally I came across an article today in the September/October edition of the US magazine Motorcycle Classics about someone upgrading the suspension on a Laverda 1000 using Race Tech kit - emulators, springs and Race Tech rear shocks. It was an interesting article - and it gave a glowing report of the success of the upgrades. I get an electronic copy of the magazine but it seems to appear in most of the bigger W H Smiths - and as it is not bagged, one can read it at one's leisure! The magazine also gave a glowing report of the new Continental Clasic attack radial tyre - has any club member tried them yet? They are supposed to improve stability a lot as well as having loads of grip.
Fear is temporary, regret is permanent: JFDI
But was falling in love with a woman 32 years my junior really a sensible move? Perhaps not, but it's been a hell of a ride!
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#22 PostAuthor: Al » Fri Sep 13, 2013 10:35 pm

Thanks Strebe for the link to Race Tech its one of many avenues i had yet to follow.
I will report back when i have ridden it but just now it has no wheels so it may be some considerable time yet, possibly early next year.

If i can help with PDQ or the specs etc, give me a shout.

AL
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#23 PostAuthor: KWACKERZ1 » Thu Sep 19, 2013 2:10 pm

The magazine also gave a glowing report of the new Continental Clasic attack radial tyre - has any club member tried them yet? They are supposed to improve stability a lot as well as having loads of grip.


I have used them this year at Mallory wetday, Spa and Cadwell, (both hot and dry days) and despite my initial reservation about fitting a 110 rear (standard size fitment) which is the skinniest tyre I have ever had on a zed.
They performed brilliantly, very sticky warmed up quick, easily as good as my am22/23 race only compound tyres I also rode on this year.

I am not the fastest rider out there but for me they were perfect, "fit and forget" which is what a good tyre should be. I would recommend them.

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#24 PostAuthor: Al » Tue Jul 15, 2014 7:20 pm

Getting on for nearly a year and i did say i would update so here goes.
Been out on only 4 trackdays with this set-up now ( two of them wet ) and initially got it all wrong and it was hideous.

Re-read and re-thought and got help from KWAKERZ1 again.
Tried a couple of different regimes and finally have found what i wanted.

Forks feel very good now and tyre wear pattern is OK.
Possibly needs a little more weight on the front tyre but apart from that i think i have arrived.

Dive is minimal, controlled and predictable.
Re-bound is firmly under control.
Pre-load and static sag seems to be just fine.
Ride height good at front and rear.
No wobbles in the corners or under braking /acceleration unless cornering half-heartedly.

Settings for anyone not asleep yet:

Rear rider (full) sag 12.5 mm
Front rider (full) sag 37.5 mm
Fork main spring pre-load 5mm (equal to the minimum recommended)
Emulator valve springs Yellow (64 Lbs / inch)
Emulator valve spring pre-load 3.5 turns.
Fork oil 20W (True S.A.E.)
Oil level is 135mm bottomed with springs out and emulators in.
16 mm of fork top leg protruding through the top yolk.
Front tyre pressure 29 PSI
Rear tyre pressure 35 P.S.I.
Tyres Conti Attack CR2
Weight at front wheel 105 KG
Weight at rear wheel 106 KG.

Had some communication with Race Tech support and they said they recommend Blue springs at two or three turns (probably suit the road) and that; in the context of the online set-up recommendations, our period of bikes with standard forks are what they refer to as 'Vintage' just so you know
:D

I suspect also that 0.95Kg/mm springs are at the top limit for my bike and its weight for track use.
0.90 or even 0.85 Kg/mm might have been a better choice, the latter suited more for fast road with a full weight bike i would hazard a guess.

Anyone done any work on bike geometry???
Looking into this as a side-line.

AL
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#25 PostAuthor: Strebe » Thu Jul 31, 2014 6:26 am

Al,
Thanks for the update. It sounds like an excellent result for not a lot of money. I think I'll give this a try on the Z1A.
What shock absorbers are you using?
Fear is temporary, regret is permanent: JFDI
But was falling in love with a woman 32 years my junior really a sensible move? Perhaps not, but it's been a hell of a ride!
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#26 PostAuthor: Al » Thu Jul 31, 2014 7:55 am

Rebuilt 20 year old Koni Dial-A-Ride's with extra spring spacers to bring the useable range back within the range of user adjustment. Oil weight has gone up grade also to slow them down and now, damping adjuster set to three out of four on the dial.
Forgot to mention weight transfer is very good now too, which has been the real underlying problem all along. Either too much or too little.
I have been working toward the set-up i have seen and spoken to people about with their 'Fast Group' bikes at various tracks i have been at.

If youre going to PDQ you could take youre front and rear springs (shocks and forks even better) as Larry has a spring compression gauge there and can measure and correct for you. If you dont want the up-rated springs i think you can use the emulators with the standard springs with a small adjustment to ride height by dropping the legs a little through the yolks.

Best of luck.

AL
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#27 PostAuthor: Coose » Thu Jun 25, 2015 8:21 am

Sorry to rekindle an old topic, but it's an interesting one if you're a geek like me! :wink:

How are you getting along with your front end Al? I need to do something with my saggy front (and the forks on my bike too!) so I'm having a trawl around to see what works for others.... :)

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#28 PostAuthor: Al » Thu Jun 25, 2015 5:28 pm

Lots of different ways to answer that as you will be aware so how about this.
I know you have been successful racing bikes at Cadwell so this may strike a chord.
From the clubhouse; a quick Right left Right (Hall Bends) and the bike stays under neath me. Not like before and i still see with others as you change sides quickly you end up sitting 'Outside' the bike and having to oversteer to get it back below you.
Hard on the brakes for the hairpin and lay it right over or the front end wants to tuck underneath but essentially no problems to report so far.
Barn and pit straight; no problems, no wobbling about, no drifting one side of the track to the other.
Flat in fourth for Coppice and without doubt my favourite part as it just digs in and goes round like the wall of death.
Charlies; is a bit odd as over the blind hill the front unloads and then its off camber so a little tentative here but still nothing that is of concern.
Park straight flat in fourth and snatch fifth just before full on the brakes and as yet have had no cause for concern even changing down whilst braking full but the back does get light and skippy here and flat in second for Park Bend just seems to flow nicely with no dramas'. I mean no dramas' like the front end rebounding after braking and making the steering vague for that right hander bend.
Chris Curve nothing to report even if changing gear whilst right over on the second part.
Gooseneck no peril there either, it doesnt mind that high speed direction change that i got previously from the standard forks / springs when i first went there.
Mansfield is a different matter; it bottoms the forks out under full brakes down hill, and that means you cant turn left until you shed a load of inertia.
I have to brake early and accelerate through the bend to get the front forks off the bottom stops and allow it to turn.
Finally the Mountain; the corner immediately before saps all youre speed so you need to accelerate hard to get up there.
The front end ploughs straight into the face and unloads quickly at the top making the front pogo into the air. If you get on the back brake in time all well and good, but if you accelerate quickly again, the second bump which is on top of the flat part will see the wheel in the air again!
My leather one piece make me look like Coco the clown or Ronald McDonald and that particular demonstration generally makes me feel like a circus act :shock:
Though to be fair i have now found a way round that, that contains an element of grace and decorum.
So reading between the lines, no issues or bad behaviors, just fun and frolicks except at the very very extremes where you need a coping strategy.
I'm still fiddling with them and was still in communication with RaceTech's technical support bloke until a week or so ago when he went very quiet. Probably had enough of my woffle.
AL
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#29 PostAuthor: Chris Riv » Thu Jun 25, 2015 6:15 pm

I went with gold emulators & linear springs all as per the info on racetech wesite, 10 weight oil, lovely comfy ride, a great improvement over std set up. This is on a std Z1. Id deffo reccomend.

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#30 PostAuthor: Coose » Thu Jun 25, 2015 7:20 pm

To be honest Al, that sounds a lot better than I would expect for an ord Zed - I would've expected a lot more issues than you've described. You're always pushing the front hard into Mansfield anyway, but I would normally take it as you do to get the drive down to the chicane and not push the front any more than you are already.

I was out on mine today and to be honest it's not that bad at all! I have no idea what's lurking in the forks, though the guy I bought the bike from said that he'd just rebuilt them with new seals and bushes. I think he may have overfilled them slightly, though not to a great extent. The sag isn't far out though not as tight as yours, which would be too little for road use if it's still as you say above.

I think the first thing I'd need to do is have a look to see what's inside...


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