"Balanced" front springs with PDS7?

AUSBERG · May 6, 2008

Hi all,
On the older progressive sprung bergs (02s, 03s etc) what front springs are a good match for a PDS7 rear spring- I imagine a set of .46s would be the go?

I currently run my 300 t 2 stroke as a PDS7/.44 combo which makes for a nice balanced bike- but unsure how the different shock angle and heavier weight of the berg would be - I imagine .44s on the front of the berg with a PDS7 rear would be way to soft?

Any comments? :?

(ps sand whoops,deep sand type riding)

Edit- should probably buy aa set of .48s and min n match with my .44s for .44,.46 & .48s.....?

Taffy · May 7, 2008

if you weigh 12 stones or 170 pounds it would be about right. just remember that even though your sag is within 3/4 mill you can be a spring out but at least the step forwards will make you happy.

regards

Taffy

bushmechanic · May 7, 2008

would be interesting to compare front/rear weight distribution of a "balanced" bike to the berg and go from there.

the 08 chassis has an extreemly high front wheel loading can't say what would work with 02, 03s but the bikes that seem to behave the best in sand whoops,deep sand type riding have a much lighter front wheel loading than mine and very stiff front springs coupled with a very plush rear eg 06 kxf450. its front springs are stock .47 and the front wheel is some 50mm further forward from the centre of mass. I guess thats why the berg racing factory guys moved their steering heads forward and so many people move their pegs back. Looking at the 09 if the crank is near the centre of mass then the front wheel loading is considerably lighter than 07, 08s.

dunno what the point of all that was, sorry. just to say that there is perhaps more to consider than it just being a 4 smoker. for example Taffy and others use stiffer front springs than KTM experts recommend. the berg is a different animal to any KTM i would think and possibly requires a different approach re F/R spring balance particulary in sand.

I'm 70kg and need about 0.46s for the nasty sand whoops so at a guess id say go the .48s at least. prolly even stiffer if the bike is really moving.

regards

Taffy · May 7, 2008

Re: RE: "Balanced" front springs with PDS7?

bushmechanic said:
would be interesting to compare front/rear weight distribution of a "balanced" bike to the berg and go from there.

the 08 chassis has an extreemly high front wheel loading can't say what would work with 02, 03s but the bikes that seem to behave the best in sand whoops,deep sand type riding have a much lighter front wheel loading than mine and very stiff front springs coupled with a very plush rear eg 06 kxf450. its front springs are stock .47 and the front wheel is some 50mm further forward from the centre of mass. I guess thats why the berg racing factory guys moved their steering heads forward and so many people move their pegs back. Looking at the 09 if the crank is near the centre of mass then the front wheel loading is considerably lighter than 07, 08s.

dunno what the point of all that was, sorry. just to say that there is perhaps more to consider than it just being a 4 smoker. for example Taffy and others use stiffer front springs than KTM experts recommend. the berg is a different animal to any KTM i would think and possibly requires a different approach re F/R spring balance particulary in sand.

I'm 70kg and need about 0.46s for the nasty sand whoops so at a guess id say go the .48s at least. prolly even stiffer if the bike is really moving.

regards

absolute music to my ears and ktmlew will have kittens over this!

yes i am on 48s and i love them. 200lb in the nud-ee!

that front end has to keep up, always up but when you get to the corner it has to go down and then some. then laid over you want the balance perfect (whereever that is?) and even having it unwind coming out of the corner you want another!

the factory boys like an extended steering head by 5 and 15mm respectively and avalo used to have a raised swing arm pivot point to create more 'rise' under acceleration ( and thus downwards pressure thus grip) the old way was to sink the rear end and as the rider was 'yawed' backwards his weight went over the back wheel.

the other thing with the present frame is that it's very hard to use less offset forks as the tyre hits the headers and the mudguard hits the frame.

if you ever saw that video of carlsson and lundqvixt riding a farmers field you could not believe the 'dip' carlsson was getting under braking. so while he had the front end out 15mm out it does tell me it was so he could have his front tyre back!!!!

it wouldn't happen to me.....

48s are wghere it's at. i just won't be telling BC that!

regards

Taffy

bushmechanic · May 7, 2008

Taffy,

from the DOC

And '07 on? The works riders have been testing a steering head some 15-25mm further away - same angle. Here is a photo of TM's ex-factory ride. Just put your vernier to the screen - it's real easy! "Joakim Ljunggren has lenghthened the frame 15mm between tank and steering head and Bjorne Carlsson 25mm the fork angle is unchanged." (Viking).

so is it 5- 15 or 15-25? Im one packet of TIG rods away from doing this mod and have raised rear shock mount basically to comphensate for the huge rear tyre and get back to "normal". shock mount may have to go back down if front wheel is moved forward.

30mm further away is getting closer to a motocross bikes weight distribution.

I think that if holding up the front is a problem becasue the front wheel needs to be further away to get what you want then stiff springs are only a bandaid and have unfortunate side effects. however never having tried moving the steering head who am I to say. even with the wheel forward I may prefer stiffer springs.

lew may indeed have kittens, or bunnies, or horses. Though If hes never tried any of this on a berg we may have to have the kittens ourselves.

It will be very interesting to learn from AUSBERG's new springs

regards

Bushie

AUSBERG · May 7, 2008

Thanks for the thoughts guys.

Got a set of .48s on the way.

BTW, rider weighs almost 100kgs, so I think the 48s might be the go. Can always mix a .48 with a .44 for .46s If .48s are too stiff ( i dont think they will be).

Bushie-just to give you an idea, ride conditions/speeds are similar to Hattah.

steve · May 7, 2008

I'm about 115-118 kg geared up and find that 44s in my 98 pretty much equivalent to the 46s I have in my 07. Weight is similar, so I assume head angle makes the difference. These are up from the 42/44 standard springs. Dunno what this means for 00-03 frames.

For the varied terrain I ride they are spot on for me. I've tried stiffer, but settled on these. Occasional gentle bottoming means that I'm using the travel, and a plush ride means control with no blisters. Pons valving of course contributes significantly.

Steve

wildman · May 14, 2008

I'm on 98 kg geared up & have 46's on my '07. Have used cable ties aroung my forks for 4 months now measuring my fork travel in different situations & finally put 1 more turn of preload on, with standard fork settings, so that bottoming is next to gone. Gets worse in summer but change to 10wt oil & adjust clickers. Love to find $300 before the Aussie force rid e & get Frank Pons to do my bike.

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"Balanced" front springs with PDS7?

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