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Old 05-08-2011, 02:05 AM   #571
DRjoe OP
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I've been having thoughts of using a linkless rear suspension set up.

I'm thinking of using a ktm swing arm and WP pds shock
For adjusting ride height I'll use a aftermarket bottom shock bush that can be set in different positions for different ride height.

The next problem is where to put the the top shock mount so that the suspension action works, I'm struggling to explain what I mean but I'm sure you get the idea.
I want to have a few different mount holes so that the angle of the shock can be altered without changing the ride height.

Does anyone know how to work out roughly where to place the shock mounts compared to the rest of the bikes geometry?

There was a good book about bike design mentioned by some one before but I forgot what it was called, Can any one tell me what it was called?

Any ideas about the linkless rear end are greatly appreciated.
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Old 05-08-2011, 02:50 AM   #572
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Thumbs down linkless are pox

link less suspension is pox! sorry mate I know you have a ktm as well but it is the truth ktm have had handling problems with the linkless rear end for years. The enduro bikes suffer badly from wanting to throw you over the bars going down hill with no trailing throttle. Conversly they climb really well. On the flat terrain they are ok until you suddenly deflect of somthing and next thing you are on the ground asking, where's my bike?

Ktm have conceeded to this on their mx bikes and they say their enduro range will not change. When you look at their adventure range you suddenly see a whole heap of linkages appear and the physical size of the swing arm is a whole lot bigger than any thing on the market.

In theory on a white board in the mattinghoffen skunk works it probably works well but in practice I am yet to ride a ktm that I have enjoyed (not bashing the brand they do many good things in other areas) as have many of my friends. I went to see a mate who is a suspension tuner and he has warned me away from a linkageless system because they are sensitive to the incorrect sag and must use the full stroke of the shock to work properly so in the case of a bike with a heavy load with a little to much sag this will affect the way the shock works.

Before you cut anthing off go seek proper advice from a reputable suspension tuner on how the bike will be tuned. I used a lazer level and set my bikes up a work stand first to make an accurate drawing of the pivot points on the bike to be copied and then during the next stage where I put the frame up and then transcribed all of the marks. There are photos in my bike build some where not sure where
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Old 05-08-2011, 03:54 AM   #573
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Thanks mate.
I'm aware the pds system is not perfect but I like its simplicity and it will make some other ideas I have a bit more possible.

Without too much work I have the rear end of my 520exc working well enough for my riding ability's.
I have never encountered the problems in the rear end that lots of good riders report of having (apart from the head shake).

The other thing is wp shocks are cheap to buy, have no linkage bearings to service and they only take a minute to swap so having one set for normal riding and one set for carrying a load is the plan.

Oh I'm more starting from scratch now rather than cutting the old frame.

thanks for your input
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Old 05-09-2011, 01:22 AM   #574
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FWIW I like my 07 650 Berg's PDS. I've never got comfortable with KTM's versions. I do however ultimately prefer the linkage rear on my 98 501 Berg, but the PDS on the 07 is 90-95% as good for me. Also, FWIW, the PDS was developed by Ohlins for Husaberg and taken over by KTM when they bought Berg, and WP.

Looking forward to how it works out.

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Old 05-09-2011, 02:01 AM   #575
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Cheers mate.
If I ever do start out riding the the stock PDS there are plenty of things to do to help.
Things like a telescopic needle and a progressive spring can apparently make huge improvement.

After some doing some research it appears the new generation ktm pds work a lot better the the older stuff, Go figure
One of the big changes is the position of shock mounts in relation to the swing arm pivot.
If I cant work out the mount points myself I'll probably copy a ktm 530 suspension and steering geometry.
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Old 05-09-2011, 02:35 AM   #576
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Quote:
Originally Posted by DRjoe View Post
Cheers mate.
If I ever do start out riding the the stock PDS there are plenty of things to do to help.
Things like a telescopic needle and a progressive spring can apparently make huge improvement.

After some doing some research it appears the new generation ktm pds work a lot better the the older stuff, Go figure
One of the big changes is the position of shock mounts in relation to the swing arm pivot.
If I cant work out the mount points myself I'll probably copy a ktm 530 suspension and steering geometry.
As I understand it the progressive springs are OK for lighter riders but create issues for riders over about 70 kg. I run a straight rate 9.6 kg/mm on my 650. My Bergs, and in particular the 650 have been my mate Frank Pons's (Biketek) late model WP fork PDS test bed so its had a few iterations and is very, very good. The 63 hp at the knobs is fun too, and it weighs 122 kg blinged and fueled ready to go. Sorry, I'm off at a tangent...

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Old 05-09-2011, 02:45 AM   #577
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I'm also running a straight rate 9.6 on my 520,
I wanted to get a progressive later on so I could try and see the difference myself.
The local guys up here (MPE suspension) couldn't tell me what would be better straight or progressive so I thought I'd just try for myself.
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Old 05-09-2011, 03:37 AM   #578
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dont do it Joe. the gearboxes arent strong enough
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Old 05-09-2011, 03:59 AM   #579
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what you talkin bout dude of the green?

Tell you what there is a load of info on road bike design on the web but nout about dirt bike design.
You type in "motorcycle frame design" into google and you get ten billion reluts about building choppers, I'm thinking that a chopper wouldn't be great for off road work.
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Old 05-09-2011, 05:50 AM   #580
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a DR with ape hangers would just give the wrong idea
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Old 05-28-2011, 12:21 AM   #581
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Does anyone know which bikes use a long flat-ish foam air filter?

I want to put the air filter under the seat so that to change it I need to remove the seat (does that make any sense?)


I'm planing on using the 690sm tank that i have and then make a new subframe tank that uses the space where the standard airbox used to be and then I'll build an airbox that runs along the top of the rear tank under the seat.

Clear as mud eh
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Old 05-28-2011, 01:40 AM   #582
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Would an Aprilia RXV one fit the bill? I don't have any pics handy but if you've seen Glen Brown's rally build you'll know what I'm talking about. And it's meant for 2 pots also!
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Old 05-28-2011, 03:28 PM   #583
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Quote:
Originally Posted by DRjoe View Post
Does anyone know which bikes use a long flat-ish foam air filter?

I want to put the air filter under the seat so that to change it I need to remove the seat (does that make any sense?)


I'm planing on using the 690sm tank that i have and then make a new subframe tank that uses the space where the standard airbox used to be and then I'll build an airbox that runs along the top of the rear tank under the seat.

Clear as mud eh
Look at some of the car/universal ones.Re useable k&n maybe.
Calculator here
http://www.knfilters.com/search/univ2.aspx?ID=S0005
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Old 05-28-2011, 05:03 PM   #584
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Cheers fellas.
I'll see if i can find Glens build thread and see what the aprilia filter looks like.
Thanks for the link Will I had a look and there are plenty that would be a perfect size but there are no foam ones.
I've tried the plastic k&N filters that you oil before on my dr and I wasn't impressed with its filtering, You could see through the filter so it aint going to stop dust and I dont like the chances of the paper element filters lasting very long in wet conditions.

Found this berg one on ebay but I cant find any dimensions for it.
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Old 05-28-2011, 05:43 PM   #585
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Sounds to me that you're copying the new Berg system. Just have a look at what's under the seat there. I liked it, not sure about water crossings though.
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