1. Overview.
1.1. This ramble describes the conversion to tapered rollers from the original cup and cone, loose ball, steering head bearings for V35 and V50, except the "Custom" models. It is intended to convey enough information to allow anyone who is capable of pulling the front end apart to be able to buy and/or have made the necessary bits, and fit them.
1.2. The summary is that it is a major job, but is not that difficult, and needn't be that expensive.
1.3. What compounds the issue is that the tapered roller bearing has to have an outrigger bearing carrier because it is a larger diameter than the original bearing.This is longer than the original cup and cone assembly, and the extra length of two bearings is more than the available length of the head stem, so a new head stem is required.
1.4. Although I have not been able to check, the new head stem length coincides perfectly with that for V65 and V50 Custom, which could be an easy way out, assuming that the critical diameters are the same. These dimensions are detailed elsewhere.
1.5. Rough Cost.
Buying the bits from a bike shop would cost to the order of $500 (Australian, I assume- ed the ed.), for which money the same place would probably fit them, so read no further.
Any of the vast number of small, backyard, engineering workshops (and the smaller the better) should make a stem for under $100, and a pair of carriers for about the same, say $220, plus $30 for the bearings, total $250. Try DMG, 03 9427 1477.
Naturally, scrounging and groveling and calling in favors and prevailing will help.
2. Propaganda, Stories, Experience, Facts, etc.
2.1. Story. Stein Dinse offers a"conversion" for $129. This is a standard tapered roller bearing in an outrigger. Uses one tapered roller in the bottom, standard cup and cone at the top. It works on the basis that there is enough head stem to cope with one tapered roller, but not two. A half-baked compromise.
2.2. Propaganda. In the original setup, the bottom bearing cops a flogging but the top doesn't. Suits the SDA story, but doesn't match experience.
2.3. Experience. If the bearing adjustment is loose, all of the load is
on the bottom bearing, but all of the slack is at the top, which rattles about- chipping, grinding and graunching, flogging out the upper bearing much more severely than the lower. Even a well-adjusted, lubricated bearing set wears the uppers more than the lowers.
2.4. Fact. Roller bearings are cheap.32005 XA with a weather seal cost me $14 at the local bearing shop.
2.5. Fact. Replacement original cup and cone bearings are obnoxiously expensive, giving little change from $400 a set.
3. Dimensions etc.
All of my measuring equipment is Imperial, save a pair of vernier calipers. Thus caliper tolerance measures are in Paris meridian type mm, precise measures in proper inches.
3.1. Headstock. A steel tube 160mm long, 40mm outside diameter, 30.6mm inside diameter, bored both ends 32.5mm diameter, 10mm deep. Slightly distorted from the welding of the frame, and painted after boring.
3.2. Headstem. The original steel stem is 240mm long, but the roller bearing setup needs a new stem at least 255mm long. There is a 28mm diameter x 5mm shoulder at the bottom end.It is a shrink fit into the bottom clamp (1.072" stem diameter x 24mm). The inner race of the bottom bearing is pressed hard against the bottom clamp, stem 0.985" diameter x 14mm.The rest of the shaft is 0.980" diameter, including the 40mm length of 25 x1mm thread at the top.
An elongated hole for the steering lock has its centre 154mm from inside of the 28mm shoulder, 159mm from the bottom of the new, 255mm, stem. Drill two 8mm holes, min. 6mm deep, each 3mm either side of centre, joined together as a slot.
Max. OD of the screw thread is 0.981", plus nothing. The top locking nut is a long nut with 25mm length of thread, and it will jam if there is insufficient clearance.
3.3. Bearing. 32005 XA, with weather seal for the top only.
3.4. Bearing Carriers. Suit frame; 1.283" diameter, 10mm long, bored through at 27mm, chamfered heavily at the top to provide a lead, and to clear the end of the counter bore in the stock.
Suit bearing; 53mm OD, approx 47mm ID, depth to suit. Note that This can be up to 5mm deeper than the bearing in order to provide some Weather protection for the bottom bearing, but needs to be feathered for the weatherseal of the top bearing.
3.5. Adjusting Nut. The bearing needs to have a screw adjustment and a locking nut. A flat washer with a long offset arm sits on top of the adjusting nut. This locks into the underside of the top clamp to prevent rotation when the long locking nut is tightened down on it. This locking nut is itself clamped by the top clamp.
The original upper cone is screw threaded. It is 0.370" deep, and the shape of the cone fits neatly inside the weather seal of 32005XA, although it is a whisker too long and so just fails to contact the weather seal on the bearing. Other than this, it makes a neat, effective, adjusting nut. I ground it back to 0.350"and it is OK." Alternatively, some trial and error should find a suitable O-ring that will fill the gap.
3.6. Drawings. I've made sketches, which I can fax. Ask. Here is a .pdf with some of them
4. Dismantling.
4.1. Getting the old bottom cone off the stem is awkward because it's a press fit up to the bottom clamp. I used a series of cold chisels, from small to FB, to wedge/lever it off, taking care not to drive into the stem proper with the sharp end.
4.2. Knock the cups out of the frame. They only need a gentle thump
applied via a long punch to the inside lip, from the opposite end.
4.3. Don't bash the stem out of the bottom clamp. Heat the clamp until it is too hot to touch, aiming the heat around the stem area, but avoid heating the stem directly to the extent possible. You can use a propane torch, or the kitchen gas ring. If using the kitchen, make sure that the sherrif is out. The stem will probably drop out of the expanded aluminum, but may need a pat with a hammer to encourage it. And it'll be hot enough to mark laminex or lino, so have a catcher for it.
5. Assembly.
5.1. While the bottom clamp is still hot, fit the replacement stem. May need to re-heat the clamp, because it will cool and contract in a few seconds. May also need a tap whilst still hot, just to make sure it's right home.
5.2. When it's cool, knock the lower inner race/cone on. This really needs some sort of drift and a firm whack. A 250mm long piece of 1" BSP water pipe will probably do this, but be sure that it strikes the end of the race and not the rollers or cage.
5.3. Clean any paint etc. out of the head stem with a pocketknife or other scraper.
5.4. Fit the bearing carriers to the head stock. Put a smear of grease on it first, and palm pressure should get it far enough in to hold. It needs to be driven using gentle pats with a big hammer, paying particular attention to see that it goes in straight, checking between blows, and then hitting to keep it straight. Don't hit the thing directly. ; Use a block of wood/brass/aluminum to protect the carrier, and hit that.
5.5. Pack the bearings with grease. This is not that easy, because the grease has to be pushed around the rollers on the cone in order to get it right in, like the liquid into the chalk.
5.6. The rest of it goes back the way it came apart.
And the steering is improved out of sight.......................
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V50 Steering Head Tapered Roller Bearing Conversion.
The original cup and cone, loose ball, steering head bearings for V35 and V50 are a sad compromise idea, short lived, maintenance intensive, and bloody expensive. Replacement original cup and cone bearings are obnoxiously expensive, giving little change from $400 a set. A far better and cheaper answer to their replacement is to convert to tapered roller bearings, as used in big block Guzzis.
Extension bearing carriers are necessary due to the roller bearing's larger diameter than the original bearing. This assembly is longer than the original cup and cone bearing, and the extra length of two bearings is more than the available length of the head stem, so a new head stem is required.
The critical bits:
All of my measuring equipment is Imperial, save a pair of vernier calipers. Thus caliper tolerance measures are in Paris meridian type mm, precise measures in proper inches.; I made the bits myself, but this is the stuff Reg does at DMG, so talk to him for pricing.
Headstem. The original steel stem is 240mm long, but the roller bearing setup needs a new stem at least 255mm long, same length as V65 and V50 Custom.; There is a 28mm diameter x 5mm shoulder at the bottom end. It is a shrink fit into the bottom clamp (1.072" stem diameter x 24mm). The inner race of the bottom bearing is pressed hard against the bottom clamp, stem 0.985" diameter x 14mm. The rest of the shaft is 0.980"diameter, including the 40mm length of 25 x1mm thread at the top. Max. OD of the screw thread is 0.981", plus nothing. The top locking nut is a long nut with 25mm length of thread, and it will jam if there is insufficient clearance.
An elongated hole for the steering lock has it's centre 154mm from inside of the 28mm shoulder, 159mm from the bottom of the new, 255mm, stem. Drill two 8mm holes, min. 6mm deep, each 3mm either side of centre, joined together as a slot.
Bearing. 32005 XA, with weather seal for the top only. $14 at the local bearing place.
Bearing Carriers. To fit frame: 1.283" diameter, 10mm long, bored
Through at 27mm, chamfered heavily at the top to provide a lead, and to clear the end of the counterbore in the stock.
To fit bearing: 53mm OD, approx 47mm ID, depth to suit. Note that this can be up to 5mm deeper than the bearing in order to provide some weather protection for the bottom bearing, but needs to be feathered for the weather seal of the top bearing.
Adjusting Nut. The bearing needs to have a screw adjustment and a locking nut. A flat washer with a long offset arm sits on top of the adjusting nut. This locks into the underside of the top clamp to prevent rotation when the long locking nut is tightened down on it. This locking nut is itself clamped by the top clamp.
The original upper cone is screw threaded. It is 0.370" deep, and the shape of the cone fits neatly inside the weather seal of 32005XA, although it is a whisker too long and so just fails to contact the weather seal on the bearing. Other than this, it makes a neat, effective, adjusting nut. I ground it back to 0.350" and it is OK. Alternatively, some trial and error should find a suitable O-ring that will fill the gap.
Drawings. I've made sketches, which I can fax. Ask.
And the steering is improved out of sight.......................
John Fergusson
